CSDMS - User contributions [en]

2026 CSDMS meeting-049

2026-03-25T17:55:58Z

Peckhams: Created page with "{{CSDMS meeting personal information template-2026 |CSDMS meeting first name=Scott |CSDMS meeting last name=Peckham |CSDMS Pronouns=he, him, his |CSDMS meeting institute=University of Colorado, Boulder |CSDMS meeting city=Boulder |CSDMS meeting country=United States |CSDMS meeting state=Colorado |CSDMS meeting email address=Scott.Peckham@colorado.edu |CSDMS meeting phone=3039569823 }} {{CSDMS meeting select clinics1 2026 |CSDMS_meeting_select_clinics1_2026=4) The Art of..."

{{CSDMS meeting personal information template-2026
|CSDMS meeting first name=Scott
|CSDMS meeting last name=Peckham
|CSDMS Pronouns=he, him, his
|CSDMS meeting institute=University of Colorado, Boulder
|CSDMS meeting city=Boulder
|CSDMS meeting country=United States
|CSDMS meeting state=Colorado
|CSDMS meeting email address=Scott.Peckham@colorado.edu
|CSDMS meeting phone=3039569823
}}
{{CSDMS meeting select clinics1 2026
|CSDMS_meeting_select_clinics1_2026=4) The Art of Modeling: From Concept to Math with Balance Equations
}}
{{CSDMS meeting select clinics2 2026
|CSDMS_meeting_select_clinics2_2026=3) Using Machine Learning for Landscape Feature Detection: Beaver Dams and Beyond!
}}
{{CSDMS meeting select clinics3 2026
|CSDMS_meeting_select_clinics3_2026=1) TopoRivBlender: Reproducible 3D Visualizations in Blender and Python
}}
{{CSDMS meeting abstract yes no 2026
|CSDMS meeting abstract submit 2026=No
}}
{{CSDMS meeting abstract poster Epub 2026}}
{{CSDMS meeting abstract title temp2026}}
{{CSDMS meeting abstract template 2026}}
{{blank line template}}

2025 CSDMS meeting-089

2025-03-20T00:23:40Z

Peckhams: Created page with "{{CSDMS meeting personal information template-2025 |CSDMS meeting first name=Scott |CSDMS meeting last name=Peckham |CSDMS Pronouns=he/his/him |CSDMS meeting institute=University of Colorado, Boulder |CSDMS meeting city=Broomfield |CSDMS meeting country=United States |CSDMS meeting state=Colorado |CSDMS meeting email address=Scott.Peckham@colorado.edu |CSDMS meeting phone=3039569823 }} {{CSDMS meeting select clinics1 2025 |CSDMS_meeting_select_clinics1_2025=4) Get lazy w..."

{{CSDMS meeting personal information template-2025
|CSDMS meeting first name=Scott
|CSDMS meeting last name=Peckham
|CSDMS Pronouns=he/his/him
|CSDMS meeting institute=University of Colorado, Boulder
|CSDMS meeting city=Broomfield
|CSDMS meeting country=United States
|CSDMS meeting state=Colorado
|CSDMS meeting email address=Scott.Peckham@colorado.edu
|CSDMS meeting phone=3039569823
}}
{{CSDMS meeting select clinics1 2025
|CSDMS_meeting_select_clinics1_2025=4) Get lazy with LLMs
}}
{{CSDMS meeting select clinics2 2025
|CSDMS_meeting_select_clinics2_2025=2) From Exploration to Publication: Geospatial Research in the Jupyter Ecosystem
}}
{{CSDMS meeting select clinics3 2025
|CSDMS_meeting_select_clinics3_2025=2) Accelerating Glacier and Surface Processes Modeling with Machine Learning and New Python Libraries
}}
{{CSDMS meeting abstract yes no 2025
|CSDMS meeting abstract submit 2025=No
}}
{{CSDMS meeting abstract poster Epub 2025}}
{{CSDMS meeting abstract title temp2025}}
{{CSDMS meeting abstract template 2025}}
{{blank line template}}

2024 CSDMS meeting-007

2024-01-19T21:05:10Z

Peckhams: Created page with "{{CSDMS meeting personal information template-2024 |CSDMS meeting first name=Scott |CSDMS meeting last name=Peckham |CSDMS Pronouns=he/him/his |CSDMS meeting institute=University of Colorado Boulder |CSDMS meeting city=Boulder |CSDMS meeting country=United States |CSDMS meeting state=Colorado |CSDMS meeting email address=Scott.Peckham@colorado.edu |CSDMS meeting phone=303-956-9823 }} {{CSDMS meeting select clinics1 2024 |CSDMS_meeting_select_clinics1_2024=3) Introduction..."

{{CSDMS meeting personal information template-2024
|CSDMS meeting first name=Scott
|CSDMS meeting last name=Peckham
|CSDMS Pronouns=he/him/his
|CSDMS meeting institute=University of Colorado Boulder
|CSDMS meeting city=Boulder
|CSDMS meeting country=United States
|CSDMS meeting state=Colorado
|CSDMS meeting email address=Scott.Peckham@colorado.edu
|CSDMS meeting phone=303-956-9823
}}
{{CSDMS meeting select clinics1 2024
|CSDMS_meeting_select_clinics1_2024=3) Introduction to agent-based modeling for socio-environmental systems
}}
{{CSDMS meeting select clinics2 2024
|CSDMS_meeting_select_clinics2_2024=2) Introduction & Building with Google Earth Engine: Batteries Included
}}
{{CSDMS meeting select clinics3 2024
|CSDMS_meeting_select_clinics3_2024=4) A Hands-On Workshop on GPU-Based Landscape Evolution Modeling
}}
{{CSDMS meeting abstract yes no 2024
|CSDMS meeting abstract submit 2024=No
}}
{{CSDMS meeting abstract poster Epub 2024}}
{{CSDMS meeting abstract title temp2024}}
{{CSDMS meeting abstract template 2024}}
{{blank line template}}

2023 CSDMS meeting-080

2023-03-16T20:10:15Z

Peckhams: Created page with "{{CSDMS meeting personal information template-2023 |CSDMS meeting first name=Scott |CSDMS meeting last name=Peckham |CSDMS Pronouns=he/him/his |CSDMS meeting institute=University of Colorado |CSDMS meeting city=Boulder |CSDMS meeting country=United States |CSDMS meeting state=Colorado |CSDMS meeting email address=Scott.Peckham@colorado.edu |CSDMS meeting phone=3039569823 }} {{CSDMS meeting select clinics1 2023 |CSDMS_meeting_select_clinics1_2023=2) Best practices open so..."

{{CSDMS meeting personal information template-2023
|CSDMS meeting first name=Scott
|CSDMS meeting last name=Peckham
|CSDMS Pronouns=he/him/his
|CSDMS meeting institute=University of Colorado
|CSDMS meeting city=Boulder
|CSDMS meeting country=United States
|CSDMS meeting state=Colorado
|CSDMS meeting email address=Scott.Peckham@colorado.edu
|CSDMS meeting phone=3039569823
}}
{{CSDMS meeting select clinics1 2023
|CSDMS_meeting_select_clinics1_2023=2) Best practices open source Python-based infrastructure
}}
{{CSDMS meeting select clinics2 2023
|CSDMS_meeting_select_clinics2_2023=1) Introduction to Landlab
}}
{{CSDMS meeting select clinics3 2023
|CSDMS_meeting_select_clinics3_2023=3) Building solvers for sustainable performance
}}
{{CSDMS meeting abstract yes no 2023
|CSDMS meeting abstract submit 2023=No
}}
{{CSDMS meeting abstract poster Epub 2023}}
{{CSDMS meeting abstract title temp2023}}
{{CSDMS meeting abstract template 2023}}
{{blank line template}}

Presenters-0530

2021-01-19T17:47:57Z

Peckhams: Created page with "{{Presenters temp |CSDMS meeting event title=CSDMS 2021: Changing Landscapes and Seascapes: Modeling for Discovery, Decision Making, and Communication |CSDMS meeting event yea..."

{{Presenters temp
|CSDMS meeting event title=CSDMS 2021: Changing Landscapes and Seascapes: Modeling for Discovery, Decision Making, and Communication
|CSDMS meeting event year=2021
|CSDMS meeting presentation type=Clinic
|CSDMS meeting first name=Scott
|CSDMS meeting last name=Peckham
|CSDMS meeting institute=University of Colorado
|Country member=United States
|CSDMS meeting state=Colorado
|CSDMS meeting email address=Scott.Peckham@colorado.edu
|CSDMS meeting title presentation=Component-based Hydrologic Modeling: Getting Started with the TopoFlow 3.6 Python Package
}}
{{Presenters presentation
|CSDMS meeting abstract presentation=TopoFlow is a plug-and-play, spatial hydrologic model distributed as an open-source Python package. The current version includes numerous hydrologic process components (all BMI-compliant), an extensive set of utilities for data preparation, river network delineation, visualization and basic calibration, the EMELI model coupling framework, sample data and a set of Jupyter notebooks for learning about the capabilities. The total package consists of around 90,000 lines of efficient code that uses NumPy and runs in Python 3.*. In this clinic, we will first cover some background information, install the package and then work through several Jupyter notebooks to explore the functionality.
|CSDMS meeting youtube code=0
|CSDMS meeting participants=0
}}
{{Presenters keywords temp
|Presentation keywords=Hydrology
}}
{{Presenters keywords temp
|Presentation keywords=River networks
}}
{{Presenters keywords temp
|Presentation keywords=Numerical methods
}}
{{Presenters keywords temp
|Presentation keywords=Jupyter Notebook
}}
{{Presenters keywords temp
|Presentation keywords=Python
}}
{{Presenters keywords temp
|Presentation keywords=Numpy
}}
{{Presenters additional material
|Working group member=Terrestrial Working Group, Education and Knowledge Transfer (EKT) Working Group, Cyberinformatics and Numerics Working Group, Hydrology Focus Research Group, Modeling Platform Interoperability Initiative, River Network Modeling Initiative
}}

CSN Operation Templates

2016-02-20T00:57:01Z

Peckhams: /* {{ Bar Heading| text=Mathematical Operators that Return Vectors}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
u_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
v_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
biharmonic_of_X (X must be a scalar field)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
nadir_angle_of_X (also called "off-nadir angle")
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_antigradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
ccw_rotation_of_X (X must be a 2D vector field)
cw_rotation_of_X (X must be a 2D vector field)
scaling_of_X (X must be a vector field)
dilation_of_X (X must be a vector field)
contraction_of_X (X must be a vector field)
translation_of_X (X must be a vector field)
azimuthal_projection_of_X (X must be a 3D vector (not a field); result is 2D)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-20T00:54:47Z

Peckhams: /* {{ Bar Heading| text=Mathematical Operators that Return Scalars}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
u_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
v_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
biharmonic_of_X (X must be a scalar field)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
nadir_angle_of_X (also called "off-nadir angle")
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_antigradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
ccw_rotation_of_X (X must be a 2D vector field)
cw_rotation_of_X (X must be a 2D vector field)
scaling_of_X (X must be a vector field)
dilation_of_X (X must be a vector field)
contraction_of_X (X must be a vector field)
translation_of_X (X must be a vector field)
azimuthal_projection_of_X (X must be a 3D vector field; result is 2D)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-20T00:49:55Z

Peckhams: /* {{ Bar Heading| text=Mathematical Operators that Return Vectors}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
u_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
v_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
nadir_angle_of_X
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
ccw_rotation_of_X (X must be a 2D vector field)
cw_rotation_of_X (X must be a 2D vector field)
scaling_of_X (X must be a vector field)
dilation_of_X (X must be a vector field)
contraction_of_X (X must be a vector field)
translation_of_X (X must be a vector field)
azimuthal_projection_of_X (X must be a 3D vector field; result is 2D)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-16T00:00:50Z

Peckhams: /* {{ Bar Heading| text=Mathematical Operators that Return Scalars}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
u_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
v_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
nadir_angle_of_X
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:58:59Z

Peckhams: /* {{ Bar Heading| text=Spatial Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
u_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
v_derivative_of_X # (for orthogonal curvilinear coordinates u and v)
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:47:06Z

Peckhams: /* {{ Bar Heading| text=Special Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
directional_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:46:51Z

Peckhams: /* {{ Bar Heading| text=Material Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Special Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X
direction_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.
:
* A '''directional derivative''' of a scalar field, F, quantifies how much F changes as we move in a direction given by some unit vector field, u. It is computed as the dot product of grad(F) and u.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:34:27Z

Peckhams: /* {{ Bar Heading| text=Material Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Material Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v. This is sometimes called the "convective derivative", but most textbook authors prefer "advective" vs. "convective" to avoid confusion.
:
* The advective derivative of a flow vector component (u, v or w) is called the "advective acceleration" (or alternately, the "convective acceleration"). The time derivative of a flow vector component is called the "local acceleration".
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:27:40Z

Peckhams: /* {{ Bar Heading| text=Material Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Material Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v.
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the (partial) time derivative of F and the advective derivative of F.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:27:07Z

Peckhams: /* {{ Bar Heading| text=Material Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Material Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v.
:
* In fluid mechanics (Eulerian description), the '''material derivative''' of F, usually denoted as "DF/Dt", is the sum of the time derivative of F and the advective derivative of F.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:26:38Z

Peckhams: /* {{ Bar Heading| text=Material Derivatives}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Material Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X

* In fluid mechanics (Eulerian description), the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v.
:
* In fluid mechanics (Eulerian description), the '''material derivative'' 's F, usually denoted as "DF/Dt", is the sum of the time derivative of F and the advective derivative of F.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Operation Templates

2016-02-15T23:25:42Z

Peckhams: /*   CSDMS Standard Names — Operation Templates */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Operation Templates''' =
:
* Operations can optionally be given as a prefix to the quantity part of an existing standard name. The prefix always ends in the word "_of", which is a reserved word. It can therefore be used as a delimiter to separate the operation from the quantity name it acts on.
:
* Applying an operation to a quantity results in a new quantity that frequently has different units than the original quantity.
:
* Operations are applied to the ''quantity'' part of the name instead of to the ''entire'' name (object + quantity) so that all standard names associated with a given object will group together alphabetically.
:
* The CSDMS Standard Names currently (Feb. 5, 2013) support the concept of a '''''quantity suffix''''' that can be applied to a base quantity to create a new quantity that usually has the same units, as in "time_step", "elevation_increment", "mass_limit", "pressure_anomaly" and "temperature_correction". However, it appears that every quantity suffix can also be expressed as an operation, so the quantity suffix concept may be discontinued.
:
* The CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).

 

== {{ Bar Heading| text=Time Derivatives}} ==

  "time_derivative_of_" (maybe we should allow "d_dt_of" ??)

:''Examples''
bedrock_surface__time_derivative_of_elevation
sea_water__time_derivative_of_north_component_of_velocity
soil__time_derivative_of_hydraulic_conductivity

* This pattern was modified on Nov. 19, 2012; "derivative_wrt_time_of" was replaced by "time_derivative_of".
:
* This pattern adds units of inverse time to the units of the quantity it acts on.
:
* This pattern is extended to higher-order derivatives by adding a prefix like "2nd_", as in: "2nd_time_derivative_of_".
:
* Should we add "material_derivative_of" as another operation? See: [http://en.wikipedia.org/wiki/Material_derivative Material derivative].
:
* Many quantity names built from process names have a sign connotation, such as "erosion_rate", "deposition_rate" and "accumulation_rate". If either sign is possible, the "time_derivative_of_X" pattern is generally less ambiguous and therefore preferable (e.g. time_derivative_of_elevation vs. erosion_rate).

 


== {{ Bar Heading| text=Spatial Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_derivative_of_X
cross-shore_derivative_of_X (or just "offshore" ??)
cross-stream_derivative_of_X
east_derivative_of_X
normal_derivative_of_X
north_derivative_of_X
offshore_derivative_of_X
streamwise_derivative_of_X
tangential_derivative_of_X
x_derivative_of_X
x_x_derivative_of_X ### (or "second_x_derivative_of_" ??)
x_y_derivative_of_X
y_derivative_of_X
y_y_derivative_of_X ### (or "second_y_derivative_of_" ??)
z_derivative_of_X

* This pattern was changed on Feb 5, 2013.
:
* Multiple derivatives can be specified as shown above, as in "x_x_derivative" vs. "x_derivative_of_x_derivative_of".
:
* Perhaps we should allow a shorthand, such as "d_dx_of_" and "d2_dx_dy_of_".
:
* The adjectives "eastward" and "northward" have been shortened to "east" and "north". (8/6/14)
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.

 


== {{ Bar Heading| text=Material Derivatives}} ==

  [ operator_name ] + "_of_"

:''Examples''
advective_derivative_of_X
material_derivative_of_X

* In fluid mechanics, in an Eulerian description of the flow, the '''advective derivative''' of a scalar fluid property, F, is defined as the dot product of grad(F) and the flow velocity, v.
:
* The "material derivative" of F, usually denoted as "DF/Dt", is the sum of the time derivative of F and the advective derivative of F.

 


== {{ Bar Heading| text=General Derivatives}} ==

  operation_pattern = "Y_derivative_of"

* This is an extension of the pattern used for time and spatial derivatives, where Y can be a one-word base quantity name like "temperature" or "pressure", or can use multiple words to avoid ambiguity, when necessary.

 


== {{ Bar Heading| text=Space and Time Integrals}} ==

  [ operator_name ] + "_of_"

:''Examples''
time_integral_of_X
time_integral_from_start_of_X
area_integral_of_X
basin_integral_of_X
domain_integral_of_X
domain_time_integral_of_X
globe_integral_of_X
line_integral_of_X
volume_integral_of_X
z_integral_of_X (for vertically-integrated quantities)

* The naming rules for integrals were modified on Nov. 19, 2012. This new pattern (shown above) is more flexible and results in shorter operation names. Single words such as "area", "domain", "line", "time" and "volume" are inserted (possibly in combination) as descriptors in front of the word "integral".
:
* A "domain_integral" is an integral over the entire model domain. It is usually an area integral and the integration is usually over the model grid cells.
:
* A "basin_integral" is an integral over an entire drainage basin. It is therefore an area integral.
:
* A "globe_integral" is an integral over an entire planetary surface. It is therefore an area integral.
:
* Notice that an integral over both space (e.g. area) and time is expressed compactly as "domain_time_integral_of", instead of a long chain like: "domain_integral_of_time_integral_of".
:
* The pattern for time integrals can include some standard limits of integration, as reserved words, such as "from_start" and "to_finish". (8/6/14) If limits of integration are not specified, time integrals are taken from the start time of a model run to the current time (when the variable is accessed).
:
* The pattern for vertical or "z" integrals can include some standard limits of integration, as reserved words, such as "from_bottom" and "to_top". (8/7/14) Bottom and top are used throughout the CSDMS Standard Names to refer to the bottom and top of a layer (e.g. snow, channel water, sea water, atmosphere). This pattern can also include the prefix '''partial''' to indicate a "partial sum", as in "partial_z_integral_of". (8/6/14)
:
* Perhaps we should allow the time interval to be given in the operation name, at least for intervals like "hour", "day" and "year". e.g.

land_surface_radiation~incoming~shortwave__one-hour_time_integral_of_energy_flux

 


== {{ Bar Heading| text=Applied Functions of One Variable}} ==

  [ function_name ] + "_of_"

:''Examples''
abs_of_X
cos_of_X
exp_of_X
half_of_X
inverse_of_X (used to specify the inverse of a function, when needed)
log_of_X (instead of "ln_X" in CF)
log10_of_X (instead of "log10_X" in CF)
minus_of_X
fourth_of_X
sin_of_X (not in CF)
sgn_of_X
sqrt_of_X (not in CF)
square_of_X (also a CF Standard Names transformation)
tan_of_X
tanh_of_X
third_of_X
0.2_power_of_X (???, or one_fifth_power_of ??)
:
* Multiplication by a floating-point number could be supported by allowing operation names like "2_of", "0.5_of" and "2_times_of".
:
* Addition and subtraction could be supported with function names like: 2_more_of and 2_less_of.
:
* The ones listed above are just examples; any function name used in mathematics would be used in the same way.

 


== {{ Bar Heading| text=Applied Functions of Two Variables}} ==

  [ function_name ] + "_of_X_and_Y"

:''Examples''
difference_of_X_and_Y
product_of_X_and_Y
quotient_of_X_and_Y
sum_of_X_and_Y

* A general power would instead be expressed with the pattern "Y_power_of_X", similar to a general derivative.
:
* The word "and" is a reserved word that acts as a delimiter between X and Y.
:
* It may be better to allow "times", "over", "minus" and "plus" to be used between X and Y, e.g. X_plus_Y.

 


== {{ Bar Heading| text=Statistical Operators}} ==

  [ operator_name ] + "_of_"

:''Examples''
1st_inverse_moment_of_pdf_of_X
2nd_inverse_moment_of_pdf_of_X
2nd_moment_of_pdf_of_X
3rd_moment_of_pdf_of_X
cdf_of_X (cumulative distribution function)
max_of_X
mean_of_X (or first_moment_of_X)
median_of_X
mid-range_of_X (= (min + max)/2
min_of_X
mode_of_X
pdf_of_X (probability density function)
range_of_X (= max - min)
standard_deviation_of_X
variance_of_X
variation_coefficient_of_X (standard deviation over mean)

* However, many quantities vary in both space and time, so an operation like "max_of" could be ambiguous. In order to address such cases, the following operation names can be used:

domain_max_of_X
domain_min_of_X
time_average_of_X
time_max_of_X (e.g. for a "peak discharge")
time_min_of_X

And perhaps also:
one-day_time_max_of_X
one-day_time_min_of_X

* Note that "time_average_of" is used instead of "time_mean_of" because it more closely follows how scientists talk.
:
* When there is interest in a "peak" value (i.e. a maximum with respect to time), there is generally also interest in the time at which that peak value occurs. For this purpose we could introduce a "time_of" operation to be combined with the "time_max_of" operation, as in: "time_of_time_max_of_volume_flux". However, the CSDMS Standard Names use the more compact "peak_time_of" operation, as in:

peak_time_of_volume_flux

* Similarly, it is not always clear how "mean_of_" should be interpreted unless extra adjectives/modifiers are used. For example, does "channel_water" + "mean_of_depth" mean the mean over: (1) a channel cross-section, (2) time, (3) the entire channel reach or (4) a grid of such values that spans the model domain? To remove this ambiguity, we use: (1) "time_mean_of" for a mean (or average) with respect to time and (2) "domain_mean_of" for a mean over the model domain. When "mean_of" occurs without the "time" or "domain" prefix, the mean is taken over the last object in the object part, as in "channel_water_x-section" + "mean_of_depth", or "channel_water" + "mean_of_depth".
:
* The operations, "cdf_of" and "pdf_of" were introduced on 8/28/14, for use in models that get a variable X from a random number generator. They can be used in constructions like:
integral_from_0_to_2_of_pdf_of_X
mean_of_pdf_of_X

 


== {{ Bar Heading| text=Mathematical Operators that Return Scalars}} ==

  [ operator_name ] + "_of_"

:''Examples''
alongshore_component_of_X
anomaly_of_X (e.g. anomaly_of_pressure; see drop and increment)
azimuth_angle_of_X (X must be a 2D or 3D vector field; returns an angle)
complement_of_X (90 - X, where X is an angle; see supplement_of below)
cross-shore_component_of_X
cross-stream_component_of_X
depression_of_X (e.g. depression_of_melting_point_temperature)
drop_of_X (e.g. drop_of_elevation, drop_of_pressure, drop_of_voltage)
divergence_of_X (X must be a vector field; returns a scalar.)
downstream_component_of_X
down_component_of_X
east_component_of_X
elevation_angle_of_X (X must be a 3D vector field; returns an angle)
increment_of_X (e.g. positive or negative change after one model time step)
laplacian_of_X (X must be a scalar field; returns a scalar.)
limit_of_X (asymptotic limiting value)
loss_of_X (e.g. loss_of_energy; maybe use "drop_of_energy" instead ?)
magnitude_of_X (X must be a vector or tensor)
north_component_of_X
offset_of_X
offshore_component_of_X
reciprocal_of_X (also called the "multiplicative inverse". "inverse" is a more general concept.)
reduction_of_X (e.g. atmosphere_aerosol_dust + reduction_of_transmittance)
scalar_potential_of_X (X must be a 2D or 3D vector field; X = grad(phi), where phi = scalar potential)
shift_of_X
streamfunction_of_X (X must be a 2D vector field; X = (phi_y, -phi_x), where phi = stream function)
supplement_of_X (180 - X, where X is an angle; see complement_of above)
up_component_of_X (### should we only use "z_component_of" ??)
u_component_of_X (orthogonal curvilinear coordinates)
v_component_of_X (orthogonal curvilinear coordinates)
x_component_of_X (Cartesian coordinates)
x_y_component_of_X (for tensors, like stress)
y_component_of_X (Cartesian coordinates)
z_component_of_X (Cartesian coordinates)
zenith_angle_of_X (X must be a 3D vector field; returns an angle)

land_surface__laplacian_of_elevation

* Note that the "magnitude_of" operation turns a vector or tensor quantity into a scalar quantity. Some magnitudes have shorter synonyms, such as speed = magnitude_of_velocity and slope = magnitude_of_gradient_of_elevation. The word "magnitude" can also work as a "quantity suffix", but should only be used as an operation.
:
* For a 2D vector field, the '''''azimuth angle''''' is just the official name for the angle in the xy-plane that is used in polar coordinates. (Depending on the context, it may be measured counter-clockwise from the x-axis, or clockwise from the north- or y-axis. A model should specify which angle convention it uses with an <assume> tag in its [[CSN_Metadata_Names | '''Model Coupling Metadata''']] (MCM) file.) (Perhaps we should insert "x_ccw_" or "north_cw_" in front of the word "azimuth"?) For a 3D vector field, it is the polar coordinates angle of the projection of the vector onto the xy plane. See [http://en.wikipedia.org/wiki/Azimuth Azimuth] and [http://en.wikipedia.org/wiki/Spherical_coordinate_system Spherical coordinate system].
:
* For a 3D vector field, the '''''zenith angle''''' (sometimes called the "polar angle") is the angle between the z-axis (zenith) and the vector at a given spatial location. (It can be computed using the dot product formula.) The '''elevation angle''' (sometimes called the "altitude angle") is the complement of the zenith angle; it is measured from the horizontal (xy) plane and is more commonly used in the geosciences than the zenith angle.
:
* Note that '''''nadir''''' (straight downward) is in the opposite direction of '''''zenith''''' (straight upward). Sometimes (e.g. when talking about the "looking angle" of a satellite) the term "off-nadir angle" is used, which is very descriptive. We could similarly use "off-zenith_angle" which seems to be more clear than "zenith_angle".
:
* The word "flow" can be used in the object part of the name as a shorthand for "flow_field". This is an example of the Object Name + Model Name Pattern, since vector components are really attributes of a mathematical model or construct, the flow field.
:
* The adjective "local" could be used for vector fields to emphasize that the angle or magnitude varies over the spatial domain.
:
* Some of these can be combined, as in "azimuth_angle_of_gradient_of_elevation". This differs from the "aspect_angle", which is associated with the downhill vs. uphill/gradient direction, and therefore differs by 180 degrees. The aspect angle is therefore equivalent to the "azimuth_angle_of_opposite_of_gradient_of_elevation". Note that "laplacian_of" should be used as a short synonym for "divergence_of_gradient_of". Note that "x_component_of_gradient_of_X" can be simplified to "x_derivative_of_X".
:
* There are also operations that act on two vector quantities and return a scalar, such as "cross_product_of_X_and_Y", "dot_product_of_X_and_Y" and "dot_product_angle_of_X_and_Y".
:
* Although both "alongshore" and "longshore" are used as synonyms, "alongshore" is used in the CSDMS Standard Names because it is less ambiguous.
:
* The term "inverse flattening ratio" is used for Earth ellipsoids, where "inverse" means "reciprocal" or "multiplicative inverse". The term "inverse" is really a more general mathematical concept -- the operation that "undoes" a given operation.

 


== {{ Bar Heading| text=Mathematical Operators that Return Vectors}} ==

  [ operator_name ] + "_of_"

:''Examples''
antigradient_of_X (X must be a scalar field; returns a vector; opposite_of_gradient_of_X)
curl_of_X (X must be a vector field; returns a vector.)
gradient_of_X (X must be a scalar field; returns a vector.)
left_normal_of_X (X must be a 2D vector field; returns the vector field rotated CCW by 90 degrees)
opposite_of_X (X must be a vector field; returns a vector.)
right_normal_of_X (X must be a 2D vector field; returns the vector field rotated CW by 90 degrees)
vector_potential_of_X (X must be a 2D or 3D vector field such that X = curl of vector_potential)
Y_degree_ccw_rotation_of_X (X must be a 2D vector field)

atmosphere_air_flow__curl_of_velocity
atmosphere_air_flow__gradient_of_pressure
bedrock_surface__antigradient_of_elevation

* These all return vectors, so if we require base quantities to be scalars they would not qualify unless combined with a scalar-producing operator like "magnitude_of_". So we could have derived quantities like: "magnitude_of_gradient_of_X".
:
* Note that the term '''antigradient''' is equivalent to (and shorter than) '''opposite_of_gradient'''. Flows are often in the direction of the antigradient of a scalar field.
:
* Note that the "laplacian_of" operation is equivalent to (but shorter than) the compound operation: "divergence_of_gradient_of_".
:
* A '''perpendicular vector field''' can be produced from a given 2D vector field by rotating either 90 degrees clockwise or counterclockwise (CCW). This is equivalent to swapping the 2 components and multiplying one of them by -1. The dot product of the original and rotated vector field will then be zero everywhere. Another way to refer to these 2 perpendicular vector fields, used here, is to use "left_normal" and "right_normal" as operations. Here, left and right are relative to the local direction of the 2D vector field.
:
* See: [http://en.wikipedia.org/wiki/Curl_(mathematics) '''Curl'''], [http://en.wikipedia.org/wiki/Divergence '''Divergence'''] and [http://en.wikipedia.org/wiki/Vector_potential '''Vector potential'''].

 


== {{ Bar Heading| text=Comparison to the CF Standard Names}} ==
:
* The [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/22/cf-standard-name-table.html '''CF Standard Names'''] were developed by Lawrence Livermore National Lab (LLNL) as standardized labels for variables stored in NetCDF files. In the CF Standard Names, the word "transformation" is used in the same sense as "operation" is used in the CSDMS Standard Names. Some of the "transformations" in the CF Standard Names are:

change_in_X_due_to_change_in_Y
correlation_of_X_with_Y
curl_of_X
derivative_of_X_wrt_Y
direction_of_X
divergence_of_X
gradient_of_X
integral_of_X_wrt_Y
magnitude_of_X
tendency_of_X (time_derivative)

* Unlike the CF transformations, the CSDMS operation templates attempt to express each operation as a prefix to a quantity name. For example, "time_derivative_of_X" is used instead of "derivative_of_X_wrt_time". This allows operations to be chained together (e.g. a time derivative and a space derivative).
:
* In CF Standard Names, there is also the transformation pattern: "integral_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to"). Bounds for the integral are given in metadata. There are currently 18 CF Standard Names that contain "integral" and 12 of these end with "_wrt_time".
:
* In CF Standard Names, a "transformation" called "tendency_of" is used to indicate a time derivative. There are 435 names that use this pattern. But it is a domain-specific term (i.e. not standard across the sciences) and therefore is not allowed in CSDMS Standard Names.
:
* In CF Standard Names, there is also the transformation pattern: "derivative_of_X_wrt_Y" and "time" is a CF Standard Name. ("wrt" = "with respect to" )
:
* In CF Standard Names, the transformation pattern for the derivative of a vector component is: "[component]_derivative_of_X". In the CSDMS Standard Names, the "component_of" and "derivative_of" operations can be combined as in "time_derivative_of_x_component_of_velocity".
:
* CF Standard Names also has the transformation pattern: "change_over_time_in_X", with bounds given in metadata.
:
* There are only 10 CF Standard Names that contain "derivative" and they do not follow a consistent pattern. Note, however, that in CF Standard Names, time derivatives start with "tendency_of" and don't contain the word "derivative".
:
* There are only 4 CF Standard Names that use the "x_derivative_of_" or "y_derivative_of_" pattern.
:
* Instead of the "change_in_X" transformation in the CF Standard Names, the CSDMS Standard Names have an "increment_of_X" operation. There is also "quantity suffix" called "increment" that can be applied to any base quantity to create a new base quantity, but this may become obsolete. See the discussion at the top of [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']].
:
* There are currently no CF Standard Names that use "correlation_of_X_with_Y", "curl_of_X" or "gradient_of_X". There are only 2 that use "divergence_of_X" and 4 that use "direction_of_X".

 

:
:
:

CSN Assumption Names

2015-11-17T17:53:22Z

Peckhams: /* {{ Bar Heading| text=Probability Distributions}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Assumption Names ''' =
:
* This document provides standardized assumption names or '''descriptors''' for use in Model Coupling Metadata (MCM) files. They are organized into groups which are (for the most part) mutually exclusive and which intend to span the types that are needed to describe a model's underlying physics. They cannot yet be said to be exhaustive but they are illustrative. The ones collected here already illustrate various language patterns that are commonly used to describe assumptions. 

* Note that '''assumption''' is meant to be taken as a broad term that can include things like ''conditions'', ''simplifications'', ''approximations'', ''limitations'', ''conventions'', ''provisos'' and other forms of clarification. 

* CSDMS encourages model developers to include as many <assume> tags in their Model Coupling Metadata (MCM) file as they feel apply to their model or to a particular input or output variable name. XML tag nesting determines the scope of an <assume> tag. For someone familiar with a particular modeling domain, the terms that have been collected here should be easily recognized and understood as part of that domain's standard terminology. 

* Given a collection of models that have Model Coupling Metadata (MCM) files which include a standardized listing of assumptions it will be straightforward to write software that allows the CSDMS modeling framework to automatically check whether two components to be coupled are compatible and alert users to potential problems or mismatches. Reports can also be generated automatically that quantify the ''degree of compatibility''. Similarly, opportunities for valid model coupling can then also be automatically identified.

 

== {{ Bar Heading| text=Boundary Condition Assumptions}} ==
:
* See: [http://en.wikipedia.org/wiki/Boundary_value_problem Boundary value problem] and [http://en.wikipedia.org/wiki/Initial_value_problem Initial value problem]. Initial conditions are also included in this section.
* These all end with "_boundary_condition".

[http://en.wikipedia.org/wiki/Cauchy_boundary_condition cauchy_boundary_condition]
clamped_boundary_condition
constant_pressure_boundary_condition
[http://en.wikipedia.org/wiki/Dirichlet_boundary_condition dirichlet_boundary_condition]
free_surface_boundary_condition
hinged_boundary_condition
moving_boundary_condition
[http://en.wikipedia.org/wiki/Mixed_boundary_condition mixed_boundary_condition]
[http://en.wikipedia.org/wiki/Neumann_boundary_condition neumann_boundary_condition]
natural_boundary_condition
no_normal_flow_boundary_condition
no_slip_boundary_condition
periodic_boundary_condition (same as "wrap-around")
pinned_boundary_condition
[http://en.wikipedia.org/wiki/Robin_boundary_condition robin_boundary_condition]
stefan_boundary_condition (See: [http://en.wikipedia.org/wiki/Stefan_problem Stefan problem].)
tidal_boundary_condition
toroidal_boundary_condition (same as "doubly periodic" ??)

 


== {{ Bar Heading| text=Conserved Quantity Assumptions}} ==
:
* These names all end in "_conserved". See [http://en.wikipedia.org/wiki/Conservation_law Conservation Law] and links therein.
* These names would usually be used within an <object> tag block which would make it clear what is being conserved (e.g. water or sediment).

angular_momentum_conserved
electric_charge_conserved
energy_conserved
linear_momentum_conserved
mass_conserved
momentum_conserved
potential_vorticity_conserved

 


== {{ Bar Heading| text=Coordinate Systems}} ==
:
* These end in "coordinate_system".
* See: [http://en.wikipedia.org/wiki/List_of_common_coordinate_transformations List of common coordinate transformations].
:
bipolar_coordinate_system
boundary-fitted_orthogonal_curvilinear_coordinate_system
cartesian_coordinate_system (same as "rectilinear")
cylindrical_coordinate_system (same as "polar" if 2D)
elliptic_coordinate_system
geographic_coordinate_system
log-polar_coordinate_system
orthogonal_curvilinear_coordinate_system
parabolic_coordinate_system
projected_coordinate_system (i.e. map projections)
right_hand_rule_coordinate_system
spherical_coordinate_system
terrain_following_vertical_coordinate_system (Same as "sigma coordinates"?? See: [http://www.ocean-modeling.org/docs.php?page=s-coordinate S-coordinate models], [http://en.wikipedia.org/wiki/Sigma_coordinate Sigma coordinates].)

 


== {{ Bar Heading| text=Georeferencing Assumptions}} ==
:
* Standard names for projections, ellipsoids and datums are available in the [http://www.epsg-registry.org EPSG Registry].
:
* Standard names for projections, ellipsoids and datums are also used in the [http://trac.osgeo.org/geotiff/ GeoTIFF Spec].
:
:

 


== {{ Bar Heading| text=Sign and Angle Conventions}} ==
:
clockwise_from_east_azimuth_convention
clockwise_from_north_azimuth_convention (all "bearing" angles, e.g. wind "from" angles)
clockwise_from_south_azimuth_convention
counter-clockwise_from_east_azimuth_convention
counter-clockwise_from_x_axis_azimuth_convention (standard math)
x-axis_directed_downwind
x-axis_directed_offshore
y-axis_directed_alongshore
z-axis_directed_downward (positive_downward)
z-axis_directed_upward (positive_upward)
z-axis_normal_to_surface



== {{ Bar Heading| text=Dimensionality Assumptions}} ==
:
* If the "richards_equation" assumption is used for infiltration, keep 1D and 3D out of the assumption name and give one of these with a separate <assume> tag.
* What about things like "1.5-dimensional" models?
:
1d
2d
3d

 

== {{ Bar Heading| text=Equations, Laws and Principles}} ==
:
* An <assume> tag should be provided for each equation that a model (or model component) uses. Most equations have standard names, as shown in the examples below.
:
* These all end in "_equation", "_law" or "_principle", except for the "law of the wall".
:

* See [http://en.wikipedia.org/wiki/Laws_of_science Wikipedia: Laws of Science] and [http://en.wikipedia.org/wiki/List_of_eponymous_laws List of Eponymous Laws].
:
adams_williamson_equation (See: [http://en.wikipedia.org/wiki/Adams–Williamson_equation Adams-Williamson equation].)
ampere_law
archimedes_principle
avogadro_law
beer_lambert_law
bernoulli_principle
biharmonic_equation
biot_savart_law
boltzman_equation
boyle_law
burgers_equation
cauchy_riemann_equations
combined_gas_law
conservation_of_energy_law ###
conservation_of_mass_law ### (same as continuity_equation)
conservation_of_momentum_law ###
coulomb_law
dalton_law
darcy_law (See: [http://en.wikipedia.org/wiki/Darcy%27s_law Darcy's law]).
darcy_weisbach_equation (See: [http://en.wikipedia.org/wiki/Darcy–Weisbach_equation Darcy-Weisbach]).
diffusion_equation
ehrenfest_equations (See: [http://en.wikipedia.org/wiki/Ehrenfest_equations Ehrenfest equations]).
eikonal_equation (See: [http://en.wikipedia.org/wiki/Eikonal_equation Eikonal equation].)
einstein_field_equations
euler_equation (inviscid flow)
euler_lagrange_equation
exner_equation
faraday_law
faxen_law
fick_law
flint_law
fresnel_equations
friedmann_equations
fourier_law
gauss_law_for_electricity
gauss_law_for_magnetism
gay_lussac_law
geodesic_equation
geometric_optics_equation
gibbs_helmholtz_equation
gibrat_law (See: [http://en.wikipedia.org/wiki/Gibrat%27s_law Gibrat's law].)
glen_stress_strain_law (Glen's Law for glacier flows, Glen (1955); nonnewtonian fluid)
hack_law
### heat_equation (use "diffusion_equation" instead)
helmholtz_equation
henry_law
horton_law
hubble_law
huygens_fresnel_principle (See: [http://en.wikipedia.org/wiki/Huygens–Fresnel_principle Huygens-Fresnel principle].)
ideal_gas_law (See: [http://en.wikipedia.org/wiki/Ideal_Gas_Law Ideal gas law]. Also an "ideal_gas_model" ??)
joule_first_law
joule_second_law
kepler_first_law_of_planetary_motion
kepler_second_law_of_planetary_motion
kepler_third_law_of_planetary_motion
kirchoff_circuit_laws [http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws Kirchoff circuit laws]
kirchoff_diffraction_formula
kirchoff_thermal_radiation_law
laplace_equation
law_of_the_wall (flow resistance)
lorentz_force_law
manning_equation (flow resistance)
mass_energy_equivalence
maxwell_equations
minimal_surface_equation
navier_stokes_equation
nernst_equation (See: [http://en.wikipedia.org/wiki/Nernst_equation Nernst equation].)
newton_first_law_of_motion
newton_law_of_cooling
newton_law_of_universal_gravitation
newton_second_law_of_motion
newton_third_law_of_motion
nonlinear_diffusion_equation ###
ohm_law
p_laplace_equation
planck_law
poiseuille_law
poisson_equation
reynolds_averaged_navier_stokes_equation
richards_equation (infiltration theory)
schroedinger_equation
snell_law
stefan_boltzmann_law
stiff_equation #### (a type, vs. a named equation)
stokes_law
thermodynamics_zeroth_law
thermodynamics_first_law
thermodynamics_second_law
thermodynamics_third_law
wien_displacement_law
young_laplace_equation
zipf_law (See: [http://en.wikipedia.org/wiki/Zipf%27s_Law Zipf's law].)

 


== {{ Bar Heading| text=Inequalities}} ==
:
* These all end in "_inequality".
:
* See [http://en.wikipedia.org/wiki/List_of_inequalities List of Inequalities (Wikipedia)].
:

 


== {{ Bar Heading| text=Identities}} ==
:
* These all end in "_identity".
:
* See [http://en.wikipedia.org/wiki/List_of_mathematical_identities List of Mathematical Identities (Wikipedia)].
:

 


== {{ Bar Heading| text=Approximations}} ==
:
* These all end in "_approximation" and some can be found in other sections.

adiabatic_approximation
binomial_approximation
born_approximation
born-huang_approximation
born-oppenheimer_approximation
boussinesq_approximation (ocean modeling)
central_field_approximation
coherent_potential_approximation
coopmans_approximation (See: [http://en.wikipedia.org/wiki/Coopmans_approximation Coopmans approximation].)
deep_water_wave_approximation
diophantine_approximation (of real numbers by rationals)
eikonal_approximation
empty-lattice_approximation
flat_space-time_approximation
first-order_approximation
fourier_series_approximation
frictionless_approximation
gaussian_approximation
gross-pitaevskii_approximation
heavy_traffic_approximation
infiltrated-depth_approximation (infiltration modeling)
kirkwood_approximation
lanczos_approximation
laurent_series_approximation
linear_approximation
local-density_approximation
low_rank_approximation
mean-field_approximation
minimax_approximation
muffin-tin_approximation
pade_approximation (of functions by rational functions)
patched-conic_approximation
percus-yevick_approximation
perturbation_series_approximation (See: [http://en.wikipedia.org/wiki/Perturbation_theory Perturbation theory].)
power-law_approximation
puiseux_series_approximation
quadratic_approximation
rigid_lid_approximation (## maybe not here?)
second-order_approximation
shallow_water_approximation
shallow_water_wave_approximation
small-angle_approximation (also, paraxial approximation)
spouge_approximation
steady-state_approximation
stirling_approximation
taylor_series_approximation
thin-lense_approximation
two-stream_approximation
wavelet_series_approximation ####
wkb_approximation

 


== {{ Bar Heading| text=Flow-Type Assumptions}} ==
:
* These names all end in "_flow".

accelerating_flow
axisymmetric_flow (in cylindrical coordinates, all theta derivatives are zero)
boundary_layer_flow
converging_flow
couette_flow (See: [http://en.wikipedia.org/wiki/Couette_Flow Couette flow]. Really a "flow model"?)
critical_flow (Froude number = 1. See subcritical & supercritical.)
depth_integrated_flow (for 3D flow to 2D flow; vs. vertically_integrated_flow)
diverging_flow
drag_induced_flow (e.g. Couette flow)
electro_osmotic_flow
fully_developed_flow (i.e. derivatives of velocity with distance in the flow direction vanish)
geostrophic_flow ###### CHECK
hele_shaw_flow (See: [http://en.wikipedia.org/wiki/Hele-Shaw_flow Hele-Shaw flow]. Really a "flow model"?)
high_froude_number_flow
high_reynolds_number_flow
hydraulically_rough_flow
hydraulically_smooth_flow
hydrostatic_flow
hypersonic_flow
inviscid_flow (of an ideal fluid with no viscosity)
isentropic_flow (both adiabatic and reversible; see isentropic_process)
laminar_flow
low_froude_number_flow
low_reynolds_number_flow
nonaccelerating_flow (i.e. the nonlinear inertial term is negligible compared to others)
nonhydrostatic_flow
no_radial_flow (i.e. in cylindrical coordinates, the r component of velocity is zero)
no_swirl_flow (i.e. in cylindrical coordinates, the theta component of velocity is zero; also non-swirling)
plug_flow (See: [http://en.wikipedia.org/wiki/Plug_flow Plug flow]. Sometimes called "piston flow".)
poiseuille_flow (See: [http://en.wikipedia.org/wiki/Poiseuille_flow]. Really a "flow model"?)
potential_flow (irrotational and inviscid, as around airfoils; See [http://en.wikipedia.org/wiki/Potential_flow Potential flow]).
pressure_induced_flow (e.g. Poiseuille flow)
separated_flow
statistically_isotropic_turbulent_flow
steady_flow (all time derivatives equal zero)
stokes_flow (same as "creeping flow"; See: [http://en.wikipedia.org/wiki/Stokes_Flow Stokes flow]).
subcritical_flow (Froude number < 1; see: [http://en.wikipedia.org/wiki/Froude_number Froude number].)
subsonic_flow
supercritical_flow (Froude_number > 1)
supersonic_flow
taylor_couette_flow (Really a flow model?)
taylor_dean_flow (Really a flow model?)
transonic_flow
turbulent_flow
unsteady_flow
variable_area_flow (include this one? see converging and diverging flow; nozzles)
viscous_flow

Note: "reynolds_averaged" is used in "reynolds_averaged_navier_stokes_equation".

 


== {{ Bar Heading| text=Fluid-Type Assumptions}} ==
:
* These names all end in "_fluid". See [http://en.wikipedia.org/wiki/Non-newtonian_fluid Non-newtonian Fluid] and links therein.

* See: [http://en.wikipedia.org/wiki/Fluid_dynamics Fluid dynamics] and links therein.

* The word "material" is often used instead of "fluid" or "solid", especially in the case of material types or models that may occur in either fluid or solid form.

* Most of these assumptions correspond to a particular functional relationship that describes how a fluid or material responds to an applied shear stress. (See: [http://en.wikipedia.org/wiki/Stress–strain_curve stress-strain curve].) These typically involve some combination of (1) shear stress (often denoted by tau or sigma), (2) time derivative of shear stress, and (3) shear strain rate (time derivative of the strain), sometimes abbreviated to "shear rate" or "strain rate" Note that strain is dimensionless and often denoted as epsilon. [http://en.wikipedia.org/wiki/Shear_stress Shear stress] (like pressure) has SI units of Pa. [http://en.wikipedia.org/wiki/Shear_rate Shear rate] (same as [http://en.wikipedia.org/wiki/Strain_rate strain rate]) has SI units of (1/s).

* Glen's Law is a power-law relationship that expresses the shear strain rate as the shear stress to a power, where the power is often n=3. It may be a special case of one of the nonnewtonian fluid types listed here.

bingham_plastic_fluid (See: [http://en.wikipedia.org/wiki/Bingham_plastic Bingham plastic]).
boger_fluid (See: [http://en.wikipedia.org/wiki/Constant_Viscosity_Elastic_(Boger)_Fluids]).
carreau_fluid (See: [http://en.wikipedia.org/wiki/Carreau_fluid]).
casson_fluid (industry standard model for molten milk chocolate)
compressible_fluid
cross_fluid (See: [http://en.wikipedia.org/wiki/Cross_fluid]).
dilatant_fluid (shear thickening fluid or STF)
first_order_fluid
herschel_bulkley_fluid (See: [http://en.wikipedia.org/wiki/Herschel-Bulkley_fluid]).
incompressible_fluid
kelvin_voigt_fluid (a linear viscoelastic model; same as "kelvin_material" ?? ######)
maxwell_fluid (a linear viscoelastic model. See: [http://en.wikipedia.org/wiki/Maxwell_material Maxwell material].)
newtonian_fluid (linear relation between shear stress and strain rate that goes through origin)
nonnewtonian_fluid
oldroyd_fluid (a linear viscoeleastic model; see [http://en.wikipedia.org/wiki/Oldroyd-B_model Oldroyd-B model].
power_law_fluid (generalized Newtonian, Ostward-de Waele)
pseudoplastic_fluid (shear thinning)
quemada_fluid (Used to model blood. See: [http://en.wikipedia.org/wiki/Hemorheology Hemorheology].)
rheopectic_fluid
second_order_fluid
super_fluid (See: [http://en.wikipedia.org/wiki/Superfluid Superfluid]).
thixotropic_fluid (See: [http://en.wikipedia.org/wiki/Thixotropy Thixotropy].)
viscoelastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastic].)
viscoplastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoplastic Viscoplastic].)

Note: Use "inviscid_flow" vs. "inviscid_fluid" and "viscous_flow" vs. "viscous_fluid".

 


== {{ Bar Heading| text=Material-Type Assumptions}} ==
:
* These names all end in "_material".

* There is sometimes a blurred semantic distinction between a "material model" (e.g. Arruda-Boyce model) and just a "material'. There are many named models (see separate section) for mathematical models of materials.

* Some types of materials can exist as either a solid or a fluid, and an extra assumption tag should be used to specify if one or the other is assumed.

* "Material" is used as a generic term. See: [http://en.wikipedia.org/wiki/Materials_science Materials science].)

amorphous_material (e.g. gel, glass; also noncrystalline_material. See: [http://en.wikipedia.org/wiki/Amorphous_solid].)
auxetic_material (See: [http://en.wikipedia.org/wiki/Auxetics Auxetics].)
bio_material (See: [http://en.wikipedia.org/wiki/Biomaterial Biomaterial].)
cauchy_elastic_material (same as simple elastic material)
ceramic_material (See: [http://en.wikipedia.org/wiki/Ceramic_materials Ceramic materials].)
composite_material (See: [http://en.wikipedia.org/wiki/Composite_materials Composite materials].)
compressible_material
crystalline_material (or solid?)
elastic_material (See: [http://en.wikipedia.org/wiki/Elasticity_(physics) Elasticity].)
elastoplastic_material
elastoviscoplastic_material (or solid?)
glass_material (amorphous solid that exhibits a glass transition. See: [http://en.wikipedia.org/wiki/Glass Glass].)
homogeneous_material
hyperelastic_material (See: [http://en.wikipedia.org/wiki/Hyperelastic_material Hyperelastic material]. Also called green elastic material and special case of cauchy elastic material.)
hypoelastic_material (See: [http://en.wikipedia.org/wiki/Hypoelastic_material Hypoelastic material]).
incompressible_material
isotropic_material
kelvin_voigt_material (See: [http://en.wikipedia.org/wiki/Kelvin-Voigt_material Kelvin-Voigt Material].)
linear_elastic_material
maxwell_material (See: [http://en.wikipedia.org/wiki/Maxwell_material].)
mohr_coulomb_material (See: [http://en.wikipedia.org/wiki/Mohr-Coulomb_theory Mohr-Coulomb theory]. Model or material type?)
nonlinear_elastic_material
plastic_material (See: [http://en.wikipedia.org/wiki/Plastic Plastic]. Compare to polymeric material.)
polymeric_material (See: [http://en.wikipedia.org/wiki/Polymer Polymer].)
semicrystalline_material
solid_material (for cases where material may be fluid or solid)
thermoelastic_material
viscoelastic_material (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastisticity].)
viscoplastic_material (See: [http://en.wikipedia.org/wiki/Viscoplasticity Viscoplasticity].)

 


== {{ Bar Heading| text=Function-Type Assumptions}} ==
:
* These names all end in "_function".
* See Geometry and Shape Assumptions.

analytic_function
bijective_function
chebyshev_polynomial_function
circle_function
complex_valued_function
constant_function
continuous_function
cosine_function
cumulative_distribution_function
daubechies_d2_wavelet_function (actually a whole family, with d2, d4, ..., d20)
decreasing_function
differentiable_function
differentiable_twice_function
dirac_delta_function
discontinuous_function
ellipse_function
exponential_function
gamma_function
gaussian_function
golden_spiral_function
haar_wavelet_function
harmonic_function
hermite_polynomial_function
hermitian_wavelet_function
holomorphic_function (very similar to "analytic_function")
hyperbola_function
identity_function
increasing_function
injective_function
inverse_function
linear_function
log_function
log_spiral_function (See: [http://en.wikipedia.org/wiki/Logarithmic_spiral Log spiral].)
logit_function (See: [http://en.wikipedia.org/wiki/Logit Logit function].)
monotonic_function
negative_function
nondecreasing_function (distinct from "increasing_function")
nonnegative_function
parabola_function (same as "quadratic_function")
periodic_function
polynomial_function
positive_function
power_law_function
probability_density_function
probit_function (See: [http://en.wikipedia.org/wiki/Probit Probit function].)
real_valued_function
ricker_wavelet_function ("mexican hat wavelet")
sawtooth_wave_function
sine_function
sqrt_function
square_wave_function (See: [http://en.wikipedia.org/wiki/Square_wave square wave].)
step_function (See: [http://en.wikipedia.org/wiki/Heaviside_step_function Heaviside step function].)
tanh_function
triangle_wave_function

See: [http://en.wikipedia.org/wiki/List_of_mathematical_functions List of mathematical functions (Wikipedia)].

Note that "multivalued_function" is a misnomer. See: [http://en.wikipedia.org/wiki/Multiple-valued_function multivalued function].)

* These are already included with Probability Distributions
beta_density_function
gompertz_function

* We could have a similar section for '''surfaces'''.
continuous_surface
differentiable_surface
differentiable_twice_surface

 


== {{ Bar Heading| text=Geometric Assumptions}} ==
:
* Most of these names end in "_shaped".
* The polygons here are assumed to be regular polygons. If they aren't, insert the adjective "irregular".
* See: [http://en.wikipedia.org/wiki/Geometry Geometry].

circle_shaped
cone_shaped
cube_shaped
cylinder_shaped
ellipse_shaped
ellipsoid_shaped (e.g. for earth)
half_plane
hexagon_shaped
hyperbola_shaped
octagon_shaped
parabola_shaped
pentagon_shaped
prism_shaped
rectangle_shaped
rhombus_shaped
semicircle_shaped (e.g. for a channel_cross_section)
sphere_shaped
square_pyramid_shaped
square_shaped
trapezoid_shaped (e.g. for a channel_cross_section)
triangular_pyramid_shaped

concave
concave_upward (long profiles)
convex

 


== {{ Bar Heading| text=Exclusions}} ==
:
* These are objects or effects that are neglected or excluded from consideration in a model.
* Only relevant/important exclusions should be reported.
* Most of these names start with "no_".
:
no_aerosols (1 in CF)
no_anthropogenic_effects
no_antrhopogenic_land_use_change (###### 1 in CF; excluding_anthropogenic_land_use_change)
no_baseflow (hydrology) (1 in CF; excluding_baseflow)
no_bioturbation
no_clouds (1 in CF)
no distributaries
no_friction
no_interception (hydrology)
no_litter (on forest floor) (1 in CF; excluding_litter)
no_longwave-radiation
no_macropores
no_overbank_flow
no_radial_flow (explained and duplicated in "Flow type assumptions")
no_rainfall
no_relativistic_effects
no_resistance
no_shadowing
no_shortwave-radiation
no_slipping
no_sloped-terrain
no_swirl_flow (explained and duplicated in "Flow type assumptions")
no_snow (1 in CF)
no_snowfall
no_tides (2 in CF)
no_turbulence
no_vegetation
## no_viscosity (use inviscid_flow)
no_waves

 


== {{ Bar Heading| text=Named Model-Type Assumptions (by Domain)}} ==
:
* These names all end in "_model".

'''Aerodynamics Models'''
clark_x_airfoil_model
clark_y_airfoil_model
clark_z_airfoil_model
eppler_1200_airfoil_model
joukowski_airfoil_model

'''Agent-Based Models'''
agent_based_model (See: [http://en.wikipedia.org/wiki/Agent_based_model Agent-based model].)
reynolds_flocking_model
schelling_segregation_model [http://web.mit.edu/rajsingh/www/lab/alife/schelling.html Schelling segregation model]

'''Atmosphere and Radiation Models'''
boussinesq_approximation (not in CF, but see for_*)
brutsaert_saturated_vapor_pressure_model
clear_sky (23 in CF)
deep_snow (1 in CF)
horizontal_plane_topography (for clear-sky radiation calculation, not in CF)
(OR zero_slope_terrain, OR no_sloped_terrain OR nonsloped_terrain ???
rigid_lid (in CF; always related to boussinesq approximation ??)
satterlund_saturated_vapor_pressure_model
sea_level_for_geoid (4 in CF)
standard_pressure (not in CF)
standard_temperature (not in CF)

'''Chemistry Models'''
atomic_shell_model
bohr_model
nuclear_shell_model (See: [http://en.wikipedia.org/wiki/Nuclear_shell_model nuclear shell model].)
rutherford_model
valence_bond_model
vespr_model (See: [http://en.wikipedia.org/wiki/VSEPR_Theory VESPR theory].)

'''Cosmological Models'''
baum_frampton_model (a cyclic model)
big_bang_model (See: [http://en.wikipedia.org/wiki/Big_bang Big bang]).
big_bounce_model
big_crunch_model
conformal_cyclic_model
cyclic_model
dark_energy_model (and dark_mass_model ?)
lambda_cdm_model (standard model of Big Bang cosmology)
steinhardt_turok_model (a cyclic model)

'''Earthquake Models'''
rough_fault_model
slider_block_model
spring_block_seismic_model
travelling_wave_model (include the word "earthquake"? ####)

'''Ecological Models'''
exponential_growth_model
food_web_model [http://en.wikipedia.org/wiki/Food_web Food web]
kolmogorov_predator_prey_model
logistic_growth_model
lotka_volterra_model [http://en.wikipedia.org/wiki/Predator-prey_interaction Lotka-Volterra]
natural_selection_model [http://en.wikipedia.org/wiki/Natural_selection Natural selection]
population_growth_model
richards_growth_model
trophic_cascade_model [http://en.wikipedia.org/wiki/Trophic_cascade Trophic cascade]

'''Fluid Dynamics Models'''
albertson_2d_turbulent_jet_model
batchelor_vortex_model
burgers_vortex_model
couette_flow_model
free_surface_vortex_model
free_vortex_model (irrotational, velocity proportional to 1/r)
goertler_2d_turbulent_jet_model
hill_spherical_vortex_model
horseshoe_vortex_model
lamb_chaplygin_dipole_vortex_model
lamb_oseen_vortex_model
peckham_2d_turbulent_jet_model
poiseuille_flow_model
rankine_vortex_model
rigid_body_vortex_model (velocity proportional to r)
taylor_couette_flow_model
taylor_dean_flow_model
taylor_green_vortex_model
tollmien_2d_turbulent_jet_model
trailing_vortex_model (or wing_tip_vortex_model)
turbulent_jet_model
vortex_ring_model

'''General Physics Models'''
double_pendulum_model (See: [http://en.wikipedia.org/wiki/Double_pendulum Double pendulum].)
foucault_pendulum_model (See: [http://en.wikipedia.org/wiki/Foucalt_Pendulum Foucault Pendulum].)
harmonic_oscillator_model
quantum_harmonic_oscillator_model
simple_pendulum_model (harmonic oscillator ? gravity pendulum?)
standard_particle_physics_model
vibrating_string_model

'''Geodynamics Models'''
:
:

'''Hydrology: Channelized Flow Models'''
d8_surface_flow_model
diffusive_wave_model ####
d_infinity_surface_flow_model ####
dynamic_wave_model
hydraulic_geometry_at_a_station_model
hydraulic_geometry_downstream_model #### (Leopold et al.)
kinematic_wave_model
law_of_the_wall_flow_resistance_model ##### ???
manning_flow_resistance_model ##### ???
mass_flux_flow_model
muskingum_flow_routing_model (routing flow through a channel network)
rational_regime_model

'''Hydrology: Evaporation (and sometimes Transpiration) Process Models'''
(See: [http://library.wrds.uwyo.edu/wrp/87-06/ch-04.html Methods for estimating ET].)
asce_standardized_evaporation_model (in CUAHSI HIS HydroModeler)
blaney_criddle_evaporation_model
debruin_evaporation_model (lakes and ponds)
energy_balance_evaporation_model
hargreaves_evaporation_model (remove the "s" in hargreaves ??)
jensen_haise_evaporation_model
kohler_nordenson_fox_evaporation_model (lakes and reservoirs)
kohler_parmele_evaporation_model
penman_evaporation_model
penman_monteith_evaporation_model
priestley_taylor_evaporation_model
shuttleworth_evaporation_model (a modified penman model)
stewart_rouse_evaporation_model (lakes and ponds)
thornthwaite_water_balance_model ########

'''Hydrology: Ground Water and Infiltration Modeling Assumptions'''
(also see dupuit_forschheimer in Modeling Methods.)
brooks_corey_soil_model ? ####
confined_aquifer ####
dupuit_assumption
homogeneous_medium (separate from isotropic ??)
horizontal_flowlines (and vertical equipotential lines)
hydraulic_gradient_equals_free_surface_gradient
hydraulic_gradient_equals_land_surface_gradient
hydraulic_gradient_invariant_with_depth
hydrostatic_pressure_head
impermeable_horizontal_base (or impermeable_boundary_at_base)
impermeable_lower_boundary (or impermeable_base)
isotropic_medium
steady_state_recharge ???
transitional_brooks_corey_soil_model ? ####
unconfined_aquifer ####
van_genuchten_soil_model ? ####

'''Hydrology: Infiltration Process Models'''
beven_infiltration_model (assumes Ks decays exponentially)
green_ampt_infiltration_model
horton_infiltration_model
infiltrated_depth_approximation (not in CF) (Used by Green-Ampt and Smith-Parlange)
(or infiltrability_depth_approximation)
philip_infiltration_model
richards_1d_infiltration_model
richards_3d_infiltration_model
scs_curve_number_infiltration_model (remove "curve number"?)
smith_parlange_infiltration_model

'''Hydrology: Snowmelt Models'''
degree_day_snowmelt_model
energy_balance_snowmelt_model

'''Hydrology: Soil Models'''
brooks_corey_soil_model
darcy_soil_model ?###### See Equations, Laws, Etc.
transitional_brooks_corey_soil_model
van_genuchten_soil_model

'''Hydrology: Surface Water Modeling Assumptions'''
bankfull_flow (or maximum inbank flow)
channel_width_less_than_model_cell_width
convergent_topography
convergent_or_divergent_topography ###### ?
d8_flow_between_cells
d_infinity_flow_between_cells
diffusive_wave
dynamic_wave
hydrologically_sound (applied to a DEM)
impermeable_surface ???
inbank_flow (an accepted term; contrast with overbank and bankfull flow)
kinematic_wave (hydraulic_slope_equals_channel_slope)
law_of_the_wall (also listed with equations)
liquid_water_equivalent (used to clarify a quantity like precipitation_rate)
manning_equation (also listed with equations)
mass_flux_method_flow_between_cells
overbank_flow
overland_flow
prismatic_channels
sheet_flow
spatially_uniform_rainfall
#### instantaneous_unit_hydrograph idea ???

'''Illumination and Shading Models'''
See: [http://en.wikipedia.org/wiki/List_of_common_shading_algorithms List of common shading algorithms].
blinn_phong_illumination_model
cook_torrance_illumination_model
flat_shading_model
gouraud_shading_model
lambert_illumination_model (lambert vs. lambertian)
minnaert_illumination_model
oren_nayer_illumination_model
phong_illumination_model
phong_shading_model
ward_anisotropic_illumination_model

'''Infiltration Models (Ventilation Models)'''
lbl_infiltration_model
sherman_grimsrud_infiltration_model

'''Nonlinear Science Models'''
aperiodic_tiling_model (See: [http://en.wikipedia.org/wiki/Aperiodic_tiling Aperiodic tiling].)
bond_percolation_model (what type of lattice ??)
cellular_automata_model
diffusion_limited_aggregation_model
dimer_model (and "double_dimer_model" ?)
ehrenfest_urn_model
fisher_droplet_model
interacting_particle_system_model
ising_model
lattice_gas_model (includes: lattice_gas_automata_model and lattice_boltzmann_model. See: [http://en.wikipedia.org/wiki/Lattice_gas_automaton Lattice gas automaton].)
logistic_map_model
penrose_tiling_model
potts_model (See: [http://en.wikipedia.org/wiki/Potts_model Potts model].)
sandpile_model (Per Bak, self-organized criticality)
self_similar_tree_model
site_percolation_model (what type of lattice ??)
voter_model

'''Ocean Models'''
deep_water_wave
edge_wave
fully_developed_sea
kelvin_wave (coastal or equatorial)
passive_scalar (e.g. temperature and salinity, perhaps suspended sediment)
### per_unit_length_of_wave_crest
rossby_wave
shallow_water_wave
shore_parallel_contours (not in CF)
stokes_wave

'''Sediment Transport Models'''
bagnold_sediment_transport_model (distinguish total load and bedload ####)
detachment_limited_sediment_transport
einstein_sediment_transport_model
komar_longshore_sediment_transport_model ####
meier_peter_mueller_sediment_transport_model
supply_limited_sediment_transport

'''Thermodynamics Models'''
black_body_model (See: [http://en.wikipedia.org/wiki/Black_body Black body].)
carnot_heat_engine_model (See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine]).
gray_body_model
white_body_model

'''Turbulence and Turbulence Closure Models'''
See: [http://en.wikipedia.org/wiki/Turbulence_modeling Turbulence modeling].
detached_eddy_simulation_model (DES)
direct_numerical_simulation_model (DNS) (Navier-Stokes solved without a turbulence model)
eddy_viscosity_model (due to Boussinesq, 1887)
k_epsilon_model (due to Jones and Launder)
k_omega_model (due to Kolmogorov ??)
kolmogorov_statistical_turbulence_model
large_eddy_simulation_model (LES) ?? #####
menter_shear_stress_transport_model
prandtl_mixing_length_model (due to Prandtl)
reynolds_averaged_navier_stokes_model (or reynolds_shear_stress_model)
smagorinsky_model (due to Smagorinsky, 1964; for sub-grid scale eddy viscosity)
spalart_allmaras_model

'''Water Wave Models'''
airy_wave_model [http://en.wikipedia.org/wiki/Airy_wave_theory Airy waves]
capillary_wave_model (type of wave vs. model for waves?)
cnoidal_wave_model [http://en.wikipedia.org/wiki/Cnoidal_wave Cnoidal waves]
kelvin_wave_model [http://en.wikipedia.org/wiki/Kelvin_wave]
korteweg_devries_solitary_wave_model
russell_solitary_wave_model
solitary_wave_model
stokes_wave_model
tsunami_wave_model

:
'''Models Not Yet Grouped'''
general_relativity_model
hagen_poiseuille (pressure drop in a pipe; laminar, viscous, incompressible)
harmonic_function (solution to Laplace equation)
hydraulic_jump
inclined_plane
power_law ####
special_relativity_model
unnamed_empirical_law ####
VSEPR (to compute molecular geometry)
boussinesq_buoyancy_approximation
dispersion_relation (could be linear)
kramers_kronig_relations

 


== {{ Bar Heading| text=Thermodynamic Process Assumptions}} ==
:
* These names all end in "_process". See: [http://en.wikipedia.org/wiki/Thermodynamic_process Wikipedia: Thermodynamic process] and links therein.

adiabatic_process (See: [http://en.wikipedia.org/wiki/Adiabatic_process Adiabatic]).
cyclic_process
diabatic_process
endoreversible_process
endothermic_process (better as adjective? absorbs energy)
exothermic_process (better as adjective? releases energy)
irreversible_process
isentropic_process (also called "reversible" ?; See: [http://en.wikipedia.org/wiki/Isentropic_process Isentropic]).
isenthalpic_process (also called "isoenthalpic"; See: [http://en.wikipedia.org/wiki/Isenthalpic Isenthalpic]).
isobaric_process
isocaloric_process
isochoric_process
isothermal_process
polytropic_process
quasistatic_process (reversible implies quasistatic, but not conversely)
reversible_process
thermal_equilibrium #### (See "black_body_model".) (See: [http://en.wikipedia.org/wiki/Thermal_equilibrium Thermal equilibrium]).

 


== {{ Bar Heading| text=Stochastic Model Assumptions}} ==
:
* Many of these end with the word "_process", which is part of the standard terminology. Many others end with "_distribution".

* See [http://en.wikipedia.org/wiki/Stochastic_process Wikipedia: Stochastic process] and [http://en.wikipedia.org/wiki/List_of_stochastic_processes_topics List of Stochastic Process Topics].

autoregressive
bernoulli_process
bessel_process
birth_death_process
blue_noise_process
branching_process
brownian_bridge_process
brownian_motion_process
buffon_needle_process
cauchy_process
chinese_restaurant_process
colored_noise_process
compound_poisson_process
contact_process
continuous_process
continuous_time_process
counting_process
coverage_process
cox_point_process
diffusion_process
dirichlet_process
discrete_process
discrete_time_process
ergodic_process
feller_process
fractional_brownian_motion_process
galton_watson_process
gaussian_white_noise_process
geometric_brownian_motion_process
grey_noise_process
homogeneous
hunt_process
independent_increments
#### independent_and_identically_distributed (use both)
infinitely_divisible_process
inhomogeneous_poisson_process
ito_diffusion_process
jump_diffusion_process
jump_process
levy_process
linear_least_squares_regression
local_time_process
markov_process
martingale_process
mckean_vlasov_process
moran_process
moving_average
negative (process?)
nonlinear_least_squares_regression
nonnegative (process?)
nonstationary_process
ornstein_uhlenbeck_process
pink_noise_process
point_process
poisson_event_process
poisson_line_process
poisson_point_process
poisson_polygon_process
poisson_process
polya_tree_process
positive (process?)
power_law_noise_process
pure_jump_process
random_multiplicative_cascade_process (is there "additive", too?)
random_tree_process
random_walk_process (symmetric or unsymmetric)
red_noise_process
renewal_process (generalization of Poisson point process)
risk_process
schramm_loewner_evolution_process (See: [http://en.wikipedia.org/wiki/Stochastic_Loewner_evolution SLE process]).
second_order_stationary_process
self_avoiding_random_walk_process
semi_markov_process
shot_noise_process (e.g. raindrops on a roof)
stable_process
stationary_process
storage_process
telegraph_process
uncorrelated
violet_noise_process
weak_stationarity_of_order_k
white_noise_process
wiener_process

 


== {{ Bar Heading| text=Probability Distributions}} ==
:
* Many of these end with the word "_distribution",
* Also see: [http://en.wikipedia.org/wiki/List_of_probability_distributions List of probability distributions] (Wikipedia).
* Most of these are '''named''' distributions, but some are a '''type''' of distribution (e.g. discrete distribution).
:
arcsine_distribution (See: [http://en.wikipedia.org/wiki/Arcsine_distribution Arcsine distribution].)
bates_distribution (See: [http://en.wikipedia.org/wiki/Bates_distribution Bates distribution].)
benford_distribution (See: [http://en.wikipedia.org/wiki/Benford%27s_law Benford's law].)
bernoulli_distribution (See: [http://en.wikipedia.org/wiki/Bernoulli_distribution Bernoulli distribution].)
beta_distribution (See: [http://en.wikipedia.org/wiki/Beta_distribution Beta distribution].)
beta-binomial_distribution (See: [http://en.wikipedia.org/wiki/Beta-binomial_distribution Beta-binomial distribution].)
beta-prime_distribution (See: [https://en.wikipedia.org/wiki/Beta_prime_distribution Beta prime distribution].)
bimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
binomial_distribution (See: [http://en.wikipedia.org/wiki/Binomial_distribution Binomial distribution].)
boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Boltzmann_distribution Boltzmann distribution].)
borel_distribution (See: [http://en.wikipedia.org/wiki/Borel_distribution Borel distribution].)
borel-tanner_distribution
burr_distribution (See: [https://en.wikipedia.org/wiki/Burr_distribution Burr distribution].)
cauchy_distribution (See: [http://en.wikipedia.org/wiki/Cauchy_distribution Cauchy distribution].)
champernowne_distribution (See: [http://en.wikipedia.org/wiki/Champernowne_distribution Champernowne distribution].)
chi-squared_distribution
continuous_distribution
continuous_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(continuous) Uniform distribution (continuous)].)
dagum_distribution (See: [https://en.wikipedia.org/wiki/Dagum_distribution Dagum distribution].)
dirichlet_distribution (See: [https://en.wikipedia.org/wiki/Dirichlet_distribution Dirichlet distribution].)
dirichlet-multinomial_distribution (See: [http://en.wikipedia.org/wiki/Dirichlet-multinomial_distribution Dirichlet-multinomial distribution].)
discrete_distribution
discrete_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(discrete) Uniform distribution (discrete)].)
elliptical_distribution (See: [http://en.wikipedia.org/wiki/Elliptical_distribution Elliptical distribution].)
erlang_distribution (See: [https://en.wikipedia.org/wiki/Erlang_distribution Erlang distribution].)
exponential_distribution (See: [http://en.wikipedia.org/wiki/Exponential_distribution Exponential distribution].)
first-contact_distribution (See: [http://en.wikipedia.org/wiki/Spherical_contact_distribution_function Spherical contact distribution].)
frechet_distribution (See: [http://en.wikipedia.org/wiki/Fréchet_distribution Frechet distribution].)
gamma_distribution (See: [http://en.wikipedia.org/wiki/Gamma_distribution Gamma distribution].)
gaussian_distribution (See: [https://en.wikipedia.org/wiki/Normal_distribution Normal distribution].)
generalized_extreme_value_distribution (See: [http://en.wikipedia.org/wiki/Generalized_extreme_value_distribution GEV distribution].)
generalized_pareto_distribution
geometric_distribution (See: [http://en.wikipedia.org/wiki/Geometric_distribution Geometric distribution].)
geometric-stable_distribution (See: [http://en.wikipedia.org/wiki/Geometric_stable_distribution Geometric stable distribution].)
gompertz_distribution (See: [http://en.wikipedia.org/wiki/Gompertz_function Gompertz function].)
gumbel_distribution (See: [http://en.wikipedia.org/wiki/Gumbel_distribution Gumbel distribution].)
half-normal_distribution (See: [http://en.wikipedia.org/wiki/Half-normal_distribution Half-normal distribution].)
hitting-time_distribution (See: [http://en.wikipedia.org/wiki/Hitting_time Hitting time].)
holtsmark_distribution (See: [http://en.wikipedia.org/wiki/Holtsmark_distribution Holtsmark distribution].)
hyperbolic_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_distribution Hyperbolic distribution].)
hyperbolic-secant_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_secant_distribution Hyperbolic secant distribution].)
hypergeometric_distribution (See: [http://en.wikipedia.org/wiki/Hypergeometric_distribution Hypergeometric distribution].)
identically_distributed ####
independently_distributed #####
inverse-gamma_distribution (See: [http://en.wikipedia.org/wiki/Inverse-gamma_distribution Inverse-gamma distribution].)
inverse-gaussian_distribution (See: [http://en.wikipedia.org/wiki/Inverse_Gaussian_distribution Inverse Gaussian distribution].)
irwin-hall_distribution (See: [http://en.wikipedia.org/wiki/Irwin–Hall_distribution Irwin-Hall distribution].)
joint-probability_distribution (See: [http://en.wikipedia.org/wiki/Joint_probability_distribution Joint probability distribution].)
kent_distribution (See: [http://en.wikipedia.org/wiki/Kent_distribution Kent distribution].)
landau_distribution (See: [http://en.wikipedia.org/wiki/Landau_distribution Landau distribution].)
laplace_distribution (See: [http://en.wikipedia.org/wiki/Laplace_distribution Laplace distribution].)
levy_distribution (See: [http://en.wikipedia.org/wiki/Lévy_distribution Levy distribution].)
log-cauchy_distribution (See: [http://en.wikipedia.org/wiki/Log-Cauchy_distribution Log-Cauchy distribution].)
log-logistic_distribution (See: [http://en.wikipedia.org/wiki/Log-logistic_distribution Log-logistic distribution].)
log-normal_distribution (See: [http://en.wikipedia.org/wiki/Log-normal_distribution Log-normal distribution].)
log-poisson_distribution
log-symmetric_distribution
logarithmic_distribution (See: [http://en.wikipedia.org/wiki/Logarithmic_distribution Logarithmic distribution].)
logistic_distribution (See: [http://en.wikipedia.org/wiki/Logistic_distribution Logistic distribution].)
logit-normal_distribution (See: [http://en.wikipedia.org/wiki/Logit-normal_distribution Logit-normal distribution].)
lomax_distribution (See: [https://en.wikipedia.org/wiki/Lomax_distribution Lomax distribution].)
maximum_entropy_probability_distribution (See: [http://en.wikipedia.org/wiki/Maximum_entropy_probability_distribution Max entropy pdf].)
maxwell-boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Maxwell–Boltzmann_distribution Maxwell-Boltzmann distribution].)
mixture_distribution (See: [http://en.wikipedia.org/wiki/Mixture_distribution Mixture distribution].)
multimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
multinomial_distribution (See: [http://en.wikipedia.org/wiki/Multinomial_distribution Multinomial distribution].)
nakagami_distribution (See: [http://en.wikipedia.org/wiki/Nakagami_distribution Nakagami distribution].)
negative-binomial_distribution (See: [http://en.wikipedia.org/wiki/Negative_binomial_distribution Negative binomial distribution].)
parabolic-fractal_distribution (See: [http://en.wikipedia.org/wiki/Parabolic_fractal_distribution Parabolic fractal distribution].)
pareto_distribution (See: [http://en.wikipedia.org/wiki/Pareto_distribution Pareto distribution].)
pascal_distribution (special case of negative binomial.)
pearson_distribution (See: [http://en.wikipedia.org/wiki/Pearson_distribution Pearson distribution].)
poisson_distribution (See: [http://en.wikipedia.org/wiki/Poisson_distribution Poisson distribution].)
poisson-binomial_distribution (See: [http://en.wikipedia.org/wiki/Poisson_binomial_distribution Poisson binomial distribution].)
polya_distribution (special case of negative binomial)
rademacher_distribution (See: [http://en.wikipedia.org/wiki/Rademacher_distribution Rademacher distribution].)
rayleigh_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_distribution Rayleigh distribution].)
rayleigh-mixture_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_mixture_distribution Rayleigh mixture distribution].)
reciprocal_distribution (See: [http://en.wikipedia.org/wiki/Reciprocal_distribution Reciprocal distribution].)
rice_distribution (See: [http://en.wikipedia.org/wiki/Rice_distribution Rice distribution].)
skellam_distribution (See: [http://en.wikipedia.org/wiki/Skellam_distribution Skellam distribution].)
skew-normal_distribution (See: [http://en.wikipedia.org/wiki/Skew_normal_distribution Skew normal distribution].)
slash_distribution (See: [http://en.wikipedia.org/wiki/Slash_distribution Slash distribution].)
stable_distribution (See: [http://en.wikipedia.org/wiki/Stable_distribution Stable distribution].)
student-t_distribution (See: [http://en.wikipedia.org/wiki/Student%27s_t-distribution Student's t-distribution].)
symmetric_distribution (See: [http://en.wikipedia.org/wiki/Symmetric_probability_distribution Symmetric distribution].)
tracy-widom_distribution (See: [http://en.wikipedia.org/wiki/Tracy–Widom_distribution Tracy-Widom distribution].)
triangular_distribution (See: [http://en.wikipedia.org/wiki/Triangular_distribution Triangular distribution].)
truncated_distribution (See: [http://en.wikipedia.org/wiki/Truncated_distribution Truncated distribution].)
tukey-lambda_distribution (See: [http://en.wikipedia.org/wiki/Tukey_lambda_distribution Tukey lambda distribution].)
u-quadratic_distribution (See: [http://en.wikipedia.org/wiki/U-quadratic_distribution U-quadratic distribution].)
unimodal_distribution
voigt_distribution (See: [http://en.wikipedia.org/wiki/Voigt_profile Voigt profile].)
von-mises_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises_distribution von Mises distribution].)
von-mises-fisher_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises–Fisher_distribution von Mises-Fisher distribution].)
weibull_distribution (See: [http://en.wikipedia.org/wiki/Weibull_distribution Weibull distribution].)
yule-simon_distribution (See: [http://en.wikipedia.org/wiki/Yule–Simon_distribution Yule-Simon distribution].)
zeta_distribution (See: [http://en.wikipedia.org/wiki/Zeta_distribution Zeta distribution].)
zipf_distribution (See: [http://en.wikipedia.org/wiki/Zipf%27s_law Zipf's law].)

 


== {{ Bar Heading| text=Statistical Operation Assumptions}} ==
:
* Perhaps this should be generalized to something like "Data Transformation Assumptions"?
* These names currently all end with "averaged".
* For ones that start with a unit of time, one of those units is assumed. A number can be inserted in front, when necessary, as in "two_day_averaged".

cell_averaged
day_averaged
depth_averaged
domain_averaged
hour_averaged
interval_averaged
month_averaged
population_averaged
sample_averaged
section_averaged
time_averaged
vertically_averaged
watershed_averaged
year_averaged

 


== {{ Bar Heading| text=Mathematical Assumptions}} ==
:
algebraic (equation)
bijection
bounded (set)
closed (set, curve)
compact (set)
complex-valued
conformal
constant_coefficients (equation or polynomial)
continuous
continuum (continuum_hypothesis ?)
contraction_mapping
countably_infinite
degenerate
differentiable
differentiable_twice
differentiable_three_times
differential (equation)
discontinuous
equal_mixed_partials
finite
fixed_point
ill-posed
infinite
injective
integer-valued
invertible
irrational
jordan_curve
linear
multiple_valued_function ### (misnomer)
negative
nonlinear
nonnegative
orthogonal
permutation
positive
projection
rational
real-valued
spatially_uniform
superposition
symmetric
time_space_substitution
uncountably_infinite
uniform
weak_solution
well-posed

 


== {{ Bar Heading| text=Numerical Grid Assumptions}} ==
:
* Most of these end with the word '''grid'''.
* The word "grid" is used to include the word "mesh".
:
adaptive_grid
arakawa_a_grid (unstaggered)
arakawa_b_grid (staggered)
arakawa_c_grid (staggered)
arakawa_d_grid (staggered, rotated 90 degrees)
arakawa_e_grid (staggered, rotated 45 degrees)
arakawa_u_component (attached to an input var)
arakawa_v_component (attached to an input var)
arakawa_w_component (attached to an input var)
block_structured_grid
boundary-fitted_grid (also called "body-fitted")
delaunay_triangle_grid
hexagon_grid
orthogonal_curvilinear_grid
rectilinear_grid
square_grid
staggered_grid (###### already in arakawa system ??)
structured_grid
triangle_grid
uniform_grid
unstructured_grid
voronoi_polygon_grid

 


== {{ Bar Heading| text=Numerical Method Assumptions}} ==
:
* These are used to describe the numerical method that a model uses to solve the equations it uses to compute variables of interest. The equations could be ODEs, PDEs, algebraic equations (e.g. root finding), etc. We probably don't need separate assumption names like "ode" and "pde" because that is implied by the equation name. See Equations, Laws and Principles for a standardized list of equation names.
* Most of these names end with "_method", "_scheme" or "_grid".
* See: [http://en.wikipedia.org/wiki/List_of_Runge–Kutta_methods List of Runge-Kutta methods].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_ordinary_differential_equations Numerical methods for ODEs].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_partial_differential_equations Numerical methods for PDEs].
:
a-stable_method
absolutely-stable_method
adams-bashforth_method
adaptive_mesh_refinement_method (See: [http://en.wikipedia.org/wiki/Adaptive_mesh_refinement Adaptive mesh refinement].)
adaptive_stepsize_method (See: [http://en.wikipedia.org/wiki/Adaptive_stepsize Adaptive stepsize].)
adjoint_state_method (See: [http://en.wikipedia.org/wiki/Adjoint_state_method Adjoint state method].)
analytic_element_method (See: [http://en.wikipedia.org/wiki/Analytic_element_method: Analytic element method]).
backward_difference_scheme
backward_euler_method (See: [http://en.wikipedia.org/wiki/Backward_Euler_method Backward Euler method].)
boundary_element_method (See: [http://en.wikipedia.org/wiki/Boundary_element_method Boundary element method].)
central_difference_scheme (See: [http://en.wikipedia.org/wiki/Central_differencing_scheme Central differencing scheme].)
characteristics_method (known as "method of characteristics")
collocation_method (See: [http://en.wikipedia.org/wiki/Collocation_method Collocation method].)
conditionally_stable_method
conjugate_gradient_method (See: [http://en.wikipedia.org/wiki/Conjugate_gradient_method Conjugate gradient method].)
consistent_method
convergent_method
crank-nicolson_method (See: [http://en.wikipedia.org/wiki/Crank–Nicolson_method Crank-Nicolson method].)
direct_numerical_solution
discrete_element_method (See: [http://en.wikipedia.org/wiki/Discrete_element_method Discrete element method].)
discrete_event_simulation (See: [http://en.wikipedia.org/wiki/Discrete_event_simulation Discrete event simulation].)
dynamic_relaxation_method (See: [http://en.wikipedia.org/wiki/Dynamic_relaxation Dynamic relaxation].)
euler_method (See: [http://en.wikipedia.org/wiki/Euler_method Euler method].) (distinguish between "forward" and "backward" with a prefix?)
explicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
fast_marching_method (See: [http://en.wikipedia.org/wiki/Fast_marching_method Fast marching method], a type of level_set_method.)
finite_difference_method (See: [http://en.wikipedia.org/wiki/Finite_difference_method Finite difference method].)
finite_element_method (See: [http://en.wikipedia.org/wiki/Finite_element_method Finite element method].)
finite_volume_method (See: [http://en.wikipedia.org/wiki/Finite_volume_method Finite volume method].)
first_order_accurate
five-point_stencil_method (See: [http://en.wikipedia.org/wiki/Five-point_stencil Five-point stencil].)
forward_difference_scheme
forward_time_centered_space_scheme (FTCS scheme)
galerkin_method (See: [http://en.wikipedia.org/wiki/Galerkin_method Galerkin method].)
gauss-legendre_method (See: [http://en.wikipedia.org/wiki/Gauss–Legendre_method Gauss-Legendre method].)
gauss-seidel_method (See: [http://en.wikipedia.org/wiki/Gauss–Seidel_method Gauss-Seidel method].)
halley_method (See: [http://en.wikipedia.org/wiki/Halley%27s_method Halley's method].)
heun_method (See: [http://en.wikipedia.org/wiki/Heun%27s_method Heun's method].)
implicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
interior_point_method (See: [http://en.wikipedia.org/wiki/Interior_point_method Interior point method].)
iterative_method (See: [http://en.wikipedia.org/wiki/Iterative_method Iterative method].)
l-stable_method (See: [http://en.wikipedia.org/wiki/L-stability L-stability].)
landweber_iteration_method (See: [http://en.wikipedia.org/wiki/Landweber_iteration Landweber iteration].)
large_eddy_simulation
lattice_boltzmann_method (See: [http://en.wikipedia.org/wiki/Lattice_Boltzmann_methods Lattice Boltzmann methods].)
lax-friedrichs_method (See: [http://en.wikipedia.org/wiki/Lax–Friedrichs_method Lax-Friedrichs method].)
lax-wendroff_method (See: [http://en.wikipedia.org/wiki/Lax–Wendroff_method Lax-Wendroff method].)
leapfrog_method
level_set_method (See: [http://en.wikipedia.org/wiki/Level_set_method Level set method].)
linear_multistep_method (See: [http://en.wikipedia.org/wiki/Linear_multistep_method Linear multistep method].)
maccormack_method (See: [http://en.wikipedia.org/wiki/MacCormack_method MacCormack method].)
meshfree_method (See: [http://en.wikipedia.org/wiki/Meshfree_methods Meshfree method].)
midpoint_method (See: [http://en.wikipedia.org/wiki/Midpoint_method Midpoint method].)
multigrid_method (See: [http://en.wikipedia.org/wiki/Multigrid_method Multigrid method].)
newton_raphson_method (See: [http://en.wikipedia.org/wiki/Newton%27s_method Newton's method]; also see "halley_method".)
numerov_method (See: [http://en.wikipedia.org/wiki/Numerov%27s_method Numerov's method].)
particle-in-cell_method (See: [http://en.wikipedia.org/wiki/Particle-in-cell Particle in cell].)
predictor-corrector_method (See: [http://en.wikipedia.org/wiki/Predictor–corrector_method Predictor-corrector method].)
rayleigh-ritz_method (See: [http://en.wikipedia.org/wiki/Rayleigh–Ritz_method Rayleigh-Ritz method].)
relatively_stable_method
relaxation_method (See: [http://en.wikipedia.org/wiki/Relaxation_(iterative_method) Relaxation (iterative method)].)
runge_kutta_method (See: [http://en.wikipedia.org/wiki/Runge–Kutta_methods Runge-Kutta methods]. There are several distinct types.)
second-order_accurate_method
shooting_method (See: [http://en.wikipedia.org/wiki/Shooting_method Shooting method].)
spectral_method (See: [http://en.wikipedia.org/wiki/Spectral_method Spectral method].)
split-step_method (See: [http://en.wikipedia.org/wiki/Split-step_method Split-step method].)
strongly_stable_method
successive_over_relaxation_method (See: [http://en.wikipedia.org/wiki/Successive_over-relaxation Successive over-relaxation].)
trapezoidal_rule_method (See: [http://en.wikipedia.org/wiki/Trapezoidal_rule_(differential_equations) Trapezoidal rule].)
unconditionally_stable_method
unstable_method
upwind_difference_scheme (See: [http://en.wikipedia.org/wiki/Upwind_differencing_scheme_for_convection Upwind difference scheme].)
upwind_first-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_second-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_third-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
verlet_integration_method (See: [http://en.wikipedia.org/wiki/Verlet_integration Verlet integration].)



== {{ Bar Heading| text=State of Matter Assumptions}} ==
:
* These can be provided when the model involves a substance (object) like water that could be in any of several possible states. See: [http://en.wikipedia.org/wiki/States_of_matter States of matter].
* Note that "liquid_equivalent" can also be inserted in quantity names such as "liquid_equivalent_precipitation_rate" to create a single quantity that can accommodate multiple states of matter.
:
gas_phase
liquid_phase
plasma_phase
solid_phase



== {{ Bar Heading| text=System State Assumptions}} ==
:
asymptotic_equilibrium
bistable
dynamic_equilibrium
equilibrium
ergodic
metastable (See: [http://en.wikipedia.org/wiki/Metastability Metastability]).
stable
static_equilibrium
steady_state
unstable
unsteady_state

 


== {{ Bar Heading| text=CF Convention Standard Name Assumptions}} ==
:
* [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/ '''CF Convention Standard Names'''] often include additional information and assumptions in the name itself. The ones in this section were found in the list of CF Standard Names and the number of occurrences found is listed in parentheses. It is not yet clear how some of these should be captured with standard assumption names.

* Many of these are '''Location Assumptions'''.

above_geoid (3 in CF)
above_land_surface (not in CF)
above_reference_datum (1 in CF)
above_reference_ellipsoid (5 in CF)
above_sea_floor (1 in CF)
above_sea_floor_surface (not in CF)
above_sea_level (1 in CF)
above_threshold (5 in CF)

at_*** (51 in CF)
at_cloud_base (1 in CFFl
at_cloud_top (3 in CF)
at_equilibrium (not in CF)
at_freezing_level (1 in CF)
at_land_surface (not in CF; e.g. air pressure)
at_maximum_upward_derivative (1 in CF)
at_saturation (4 in CF)
at_sea_floor (3 in CF)
at_sea_floor_surface (not in CF; e.g. water pressure)
at_sea_ice_base (8 in CF)
at_sea_level (1 in CF)
at_top_of_*** (3 in CF)
at_bottom_*** (not in CF)

assuming_*** (33 in CF)
assuming_clear_sky (24 in CF)
assuming_deep_snow (1 in CF, for surface_albedo)
assuming_no_aerosol_or_cloud (1 in CF)
assuming_no_snow (1 in CF, for surface_albedo)
assuming_no_tide (2 in CF)
assuming_sea_level_for_geoid (4 in CF)

below_geoid (1 in CF)
below_sea_level (1 in CF)
below_sea_surface (1 in CF)
below_surface (1 in CF)
below_threshold (3 in CF)

between_air_and_sea_water (1 in CF)
between_sea_water_and_air (2 in CF)

due_to_*** (399 in CF)
due_to_all_land_processes (2 in CF)
due_to_convective_cloud (1 in CF)
due_to_diffusion (18 in CF)
due_to_dry_convection (1 in CF)
due_to_dry_deposition (35 in CF)
due_to_dry_troposphere (1 in CF)
due_to_dust_ambient_aerosol (2 in CF)
due_to_emission_from_grazing (in CF)

excluding_anthropogenic_land_use_change (in CF)
excluding_baseflow (in CF)
excluding_litter (in CF)

expressed_as_*** (140 in CF)
expressed_as_carbon (67 in CF)
expressed_as_chlorine (7 in CF)
expressed_as_nitrogen (24 in CF)

for_*** (13 in CF)
for_biomass_growth (1 in CF)
for_biomass_maintenance (1 in CF)
for_boussinesq_approximation (1 in CF)
for_momentum (2 in CF; both "for_momentum_in_air")

per_capita
per_unit_area (already used in CF)
per_unit_length_of_wave_crest
per_unit_mass (already used in CF, and synonym for "specific")
per_unit_time ??
per_unit_width (e.g. discharge_per_unit_width)
(see CF: sea_water_transport_across_line,
and "transport_across_unit_distance")

:
:
:

CSN Assumption Names

2015-11-13T00:12:14Z

Peckhams: /* {{ Bar Heading| text=Probability Distributions}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Assumption Names ''' =
:
* This document provides standardized assumption names or '''descriptors''' for use in Model Coupling Metadata (MCM) files. They are organized into groups which are (for the most part) mutually exclusive and which intend to span the types that are needed to describe a model's underlying physics. They cannot yet be said to be exhaustive but they are illustrative. The ones collected here already illustrate various language patterns that are commonly used to describe assumptions. 

* Note that '''assumption''' is meant to be taken as a broad term that can include things like ''conditions'', ''simplifications'', ''approximations'', ''limitations'', ''conventions'', ''provisos'' and other forms of clarification. 

* CSDMS encourages model developers to include as many <assume> tags in their Model Coupling Metadata (MCM) file as they feel apply to their model or to a particular input or output variable name. XML tag nesting determines the scope of an <assume> tag. For someone familiar with a particular modeling domain, the terms that have been collected here should be easily recognized and understood as part of that domain's standard terminology. 

* Given a collection of models that have Model Coupling Metadata (MCM) files which include a standardized listing of assumptions it will be straightforward to write software that allows the CSDMS modeling framework to automatically check whether two components to be coupled are compatible and alert users to potential problems or mismatches. Reports can also be generated automatically that quantify the ''degree of compatibility''. Similarly, opportunities for valid model coupling can then also be automatically identified.

 

== {{ Bar Heading| text=Boundary Condition Assumptions}} ==
:
* See: [http://en.wikipedia.org/wiki/Boundary_value_problem Boundary value problem] and [http://en.wikipedia.org/wiki/Initial_value_problem Initial value problem]. Initial conditions are also included in this section.
* These all end with "_boundary_condition".

[http://en.wikipedia.org/wiki/Cauchy_boundary_condition cauchy_boundary_condition]
clamped_boundary_condition
constant_pressure_boundary_condition
[http://en.wikipedia.org/wiki/Dirichlet_boundary_condition dirichlet_boundary_condition]
free_surface_boundary_condition
hinged_boundary_condition
moving_boundary_condition
[http://en.wikipedia.org/wiki/Mixed_boundary_condition mixed_boundary_condition]
[http://en.wikipedia.org/wiki/Neumann_boundary_condition neumann_boundary_condition]
natural_boundary_condition
no_normal_flow_boundary_condition
no_slip_boundary_condition
periodic_boundary_condition (same as "wrap-around")
pinned_boundary_condition
[http://en.wikipedia.org/wiki/Robin_boundary_condition robin_boundary_condition]
stefan_boundary_condition (See: [http://en.wikipedia.org/wiki/Stefan_problem Stefan problem].)
tidal_boundary_condition
toroidal_boundary_condition (same as "doubly periodic" ??)

 


== {{ Bar Heading| text=Conserved Quantity Assumptions}} ==
:
* These names all end in "_conserved". See [http://en.wikipedia.org/wiki/Conservation_law Conservation Law] and links therein.
* These names would usually be used within an <object> tag block which would make it clear what is being conserved (e.g. water or sediment).

angular_momentum_conserved
electric_charge_conserved
energy_conserved
linear_momentum_conserved
mass_conserved
momentum_conserved
potential_vorticity_conserved

 


== {{ Bar Heading| text=Coordinate Systems}} ==
:
* These end in "coordinate_system".
* See: [http://en.wikipedia.org/wiki/List_of_common_coordinate_transformations List of common coordinate transformations].
:
bipolar_coordinate_system
boundary-fitted_orthogonal_curvilinear_coordinate_system
cartesian_coordinate_system (same as "rectilinear")
cylindrical_coordinate_system (same as "polar" if 2D)
elliptic_coordinate_system
geographic_coordinate_system
log-polar_coordinate_system
orthogonal_curvilinear_coordinate_system
parabolic_coordinate_system
projected_coordinate_system (i.e. map projections)
right_hand_rule_coordinate_system
spherical_coordinate_system
terrain_following_vertical_coordinate_system (Same as "sigma coordinates"?? See: [http://www.ocean-modeling.org/docs.php?page=s-coordinate S-coordinate models], [http://en.wikipedia.org/wiki/Sigma_coordinate Sigma coordinates].)

 


== {{ Bar Heading| text=Georeferencing Assumptions}} ==
:
* Standard names for projections, ellipsoids and datums are available in the [http://www.epsg-registry.org EPSG Registry].
:
* Standard names for projections, ellipsoids and datums are also used in the [http://trac.osgeo.org/geotiff/ GeoTIFF Spec].
:
:

 


== {{ Bar Heading| text=Sign and Angle Conventions}} ==
:
clockwise_from_east_azimuth_convention
clockwise_from_north_azimuth_convention (all "bearing" angles, e.g. wind "from" angles)
clockwise_from_south_azimuth_convention
counter-clockwise_from_east_azimuth_convention
counter-clockwise_from_x_axis_azimuth_convention (standard math)
x-axis_directed_downwind
x-axis_directed_offshore
y-axis_directed_alongshore
z-axis_directed_downward (positive_downward)
z-axis_directed_upward (positive_upward)
z-axis_normal_to_surface



== {{ Bar Heading| text=Dimensionality Assumptions}} ==
:
* If the "richards_equation" assumption is used for infiltration, keep 1D and 3D out of the assumption name and give one of these with a separate <assume> tag.
* What about things like "1.5-dimensional" models?
:
1d
2d
3d

 

== {{ Bar Heading| text=Equations, Laws and Principles}} ==
:
* An <assume> tag should be provided for each equation that a model (or model component) uses. Most equations have standard names, as shown in the examples below.
:
* These all end in "_equation", "_law" or "_principle", except for the "law of the wall".
:

* See [http://en.wikipedia.org/wiki/Laws_of_science Wikipedia: Laws of Science] and [http://en.wikipedia.org/wiki/List_of_eponymous_laws List of Eponymous Laws].
:
adams_williamson_equation (See: [http://en.wikipedia.org/wiki/Adams–Williamson_equation Adams-Williamson equation].)
ampere_law
archimedes_principle
avogadro_law
beer_lambert_law
bernoulli_principle
biharmonic_equation
biot_savart_law
boltzman_equation
boyle_law
burgers_equation
cauchy_riemann_equations
combined_gas_law
conservation_of_energy_law ###
conservation_of_mass_law ### (same as continuity_equation)
conservation_of_momentum_law ###
coulomb_law
dalton_law
darcy_law (See: [http://en.wikipedia.org/wiki/Darcy%27s_law Darcy's law]).
darcy_weisbach_equation (See: [http://en.wikipedia.org/wiki/Darcy–Weisbach_equation Darcy-Weisbach]).
diffusion_equation
ehrenfest_equations (See: [http://en.wikipedia.org/wiki/Ehrenfest_equations Ehrenfest equations]).
eikonal_equation (See: [http://en.wikipedia.org/wiki/Eikonal_equation Eikonal equation].)
einstein_field_equations
euler_equation (inviscid flow)
euler_lagrange_equation
exner_equation
faraday_law
faxen_law
fick_law
flint_law
fresnel_equations
friedmann_equations
fourier_law
gauss_law_for_electricity
gauss_law_for_magnetism
gay_lussac_law
geodesic_equation
geometric_optics_equation
gibbs_helmholtz_equation
gibrat_law (See: [http://en.wikipedia.org/wiki/Gibrat%27s_law Gibrat's law].)
glen_stress_strain_law (Glen's Law for glacier flows, Glen (1955); nonnewtonian fluid)
hack_law
### heat_equation (use "diffusion_equation" instead)
helmholtz_equation
henry_law
horton_law
hubble_law
huygens_fresnel_principle (See: [http://en.wikipedia.org/wiki/Huygens–Fresnel_principle Huygens-Fresnel principle].)
ideal_gas_law (See: [http://en.wikipedia.org/wiki/Ideal_Gas_Law Ideal gas law]. Also an "ideal_gas_model" ??)
joule_first_law
joule_second_law
kepler_first_law_of_planetary_motion
kepler_second_law_of_planetary_motion
kepler_third_law_of_planetary_motion
kirchoff_circuit_laws [http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws Kirchoff circuit laws]
kirchoff_diffraction_formula
kirchoff_thermal_radiation_law
laplace_equation
law_of_the_wall (flow resistance)
lorentz_force_law
manning_equation (flow resistance)
mass_energy_equivalence
maxwell_equations
minimal_surface_equation
navier_stokes_equation
nernst_equation (See: [http://en.wikipedia.org/wiki/Nernst_equation Nernst equation].)
newton_first_law_of_motion
newton_law_of_cooling
newton_law_of_universal_gravitation
newton_second_law_of_motion
newton_third_law_of_motion
nonlinear_diffusion_equation ###
ohm_law
p_laplace_equation
planck_law
poiseuille_law
poisson_equation
reynolds_averaged_navier_stokes_equation
richards_equation (infiltration theory)
schroedinger_equation
snell_law
stefan_boltzmann_law
stiff_equation #### (a type, vs. a named equation)
stokes_law
thermodynamics_zeroth_law
thermodynamics_first_law
thermodynamics_second_law
thermodynamics_third_law
wien_displacement_law
young_laplace_equation
zipf_law (See: [http://en.wikipedia.org/wiki/Zipf%27s_Law Zipf's law].)

 


== {{ Bar Heading| text=Inequalities}} ==
:
* These all end in "_inequality".
:
* See [http://en.wikipedia.org/wiki/List_of_inequalities List of Inequalities (Wikipedia)].
:

 


== {{ Bar Heading| text=Identities}} ==
:
* These all end in "_identity".
:
* See [http://en.wikipedia.org/wiki/List_of_mathematical_identities List of Mathematical Identities (Wikipedia)].
:

 


== {{ Bar Heading| text=Approximations}} ==
:
* These all end in "_approximation" and some can be found in other sections.

adiabatic_approximation
binomial_approximation
born_approximation
born-huang_approximation
born-oppenheimer_approximation
boussinesq_approximation (ocean modeling)
central_field_approximation
coherent_potential_approximation
coopmans_approximation (See: [http://en.wikipedia.org/wiki/Coopmans_approximation Coopmans approximation].)
deep_water_wave_approximation
diophantine_approximation (of real numbers by rationals)
eikonal_approximation
empty-lattice_approximation
flat_space-time_approximation
first-order_approximation
fourier_series_approximation
frictionless_approximation
gaussian_approximation
gross-pitaevskii_approximation
heavy_traffic_approximation
infiltrated-depth_approximation (infiltration modeling)
kirkwood_approximation
lanczos_approximation
laurent_series_approximation
linear_approximation
local-density_approximation
low_rank_approximation
mean-field_approximation
minimax_approximation
muffin-tin_approximation
pade_approximation (of functions by rational functions)
patched-conic_approximation
percus-yevick_approximation
perturbation_series_approximation (See: [http://en.wikipedia.org/wiki/Perturbation_theory Perturbation theory].)
power-law_approximation
puiseux_series_approximation
quadratic_approximation
rigid_lid_approximation (## maybe not here?)
second-order_approximation
shallow_water_approximation
shallow_water_wave_approximation
small-angle_approximation (also, paraxial approximation)
spouge_approximation
steady-state_approximation
stirling_approximation
taylor_series_approximation
thin-lense_approximation
two-stream_approximation
wavelet_series_approximation ####
wkb_approximation

 


== {{ Bar Heading| text=Flow-Type Assumptions}} ==
:
* These names all end in "_flow".

accelerating_flow
axisymmetric_flow (in cylindrical coordinates, all theta derivatives are zero)
boundary_layer_flow
converging_flow
couette_flow (See: [http://en.wikipedia.org/wiki/Couette_Flow Couette flow]. Really a "flow model"?)
critical_flow (Froude number = 1. See subcritical & supercritical.)
depth_integrated_flow (for 3D flow to 2D flow; vs. vertically_integrated_flow)
diverging_flow
drag_induced_flow (e.g. Couette flow)
electro_osmotic_flow
fully_developed_flow (i.e. derivatives of velocity with distance in the flow direction vanish)
geostrophic_flow ###### CHECK
hele_shaw_flow (See: [http://en.wikipedia.org/wiki/Hele-Shaw_flow Hele-Shaw flow]. Really a "flow model"?)
high_froude_number_flow
high_reynolds_number_flow
hydraulically_rough_flow
hydraulically_smooth_flow
hydrostatic_flow
hypersonic_flow
inviscid_flow (of an ideal fluid with no viscosity)
isentropic_flow (both adiabatic and reversible; see isentropic_process)
laminar_flow
low_froude_number_flow
low_reynolds_number_flow
nonaccelerating_flow (i.e. the nonlinear inertial term is negligible compared to others)
nonhydrostatic_flow
no_radial_flow (i.e. in cylindrical coordinates, the r component of velocity is zero)
no_swirl_flow (i.e. in cylindrical coordinates, the theta component of velocity is zero; also non-swirling)
plug_flow (See: [http://en.wikipedia.org/wiki/Plug_flow Plug flow]. Sometimes called "piston flow".)
poiseuille_flow (See: [http://en.wikipedia.org/wiki/Poiseuille_flow]. Really a "flow model"?)
potential_flow (irrotational and inviscid, as around airfoils; See [http://en.wikipedia.org/wiki/Potential_flow Potential flow]).
pressure_induced_flow (e.g. Poiseuille flow)
separated_flow
statistically_isotropic_turbulent_flow
steady_flow (all time derivatives equal zero)
stokes_flow (same as "creeping flow"; See: [http://en.wikipedia.org/wiki/Stokes_Flow Stokes flow]).
subcritical_flow (Froude number < 1; see: [http://en.wikipedia.org/wiki/Froude_number Froude number].)
subsonic_flow
supercritical_flow (Froude_number > 1)
supersonic_flow
taylor_couette_flow (Really a flow model?)
taylor_dean_flow (Really a flow model?)
transonic_flow
turbulent_flow
unsteady_flow
variable_area_flow (include this one? see converging and diverging flow; nozzles)
viscous_flow

Note: "reynolds_averaged" is used in "reynolds_averaged_navier_stokes_equation".

 


== {{ Bar Heading| text=Fluid-Type Assumptions}} ==
:
* These names all end in "_fluid". See [http://en.wikipedia.org/wiki/Non-newtonian_fluid Non-newtonian Fluid] and links therein.

* See: [http://en.wikipedia.org/wiki/Fluid_dynamics Fluid dynamics] and links therein.

* The word "material" is often used instead of "fluid" or "solid", especially in the case of material types or models that may occur in either fluid or solid form.

* Most of these assumptions correspond to a particular functional relationship that describes how a fluid or material responds to an applied shear stress. (See: [http://en.wikipedia.org/wiki/Stress–strain_curve stress-strain curve].) These typically involve some combination of (1) shear stress (often denoted by tau or sigma), (2) time derivative of shear stress, and (3) shear strain rate (time derivative of the strain), sometimes abbreviated to "shear rate" or "strain rate" Note that strain is dimensionless and often denoted as epsilon. [http://en.wikipedia.org/wiki/Shear_stress Shear stress] (like pressure) has SI units of Pa. [http://en.wikipedia.org/wiki/Shear_rate Shear rate] (same as [http://en.wikipedia.org/wiki/Strain_rate strain rate]) has SI units of (1/s).

* Glen's Law is a power-law relationship that expresses the shear strain rate as the shear stress to a power, where the power is often n=3. It may be a special case of one of the nonnewtonian fluid types listed here.

bingham_plastic_fluid (See: [http://en.wikipedia.org/wiki/Bingham_plastic Bingham plastic]).
boger_fluid (See: [http://en.wikipedia.org/wiki/Constant_Viscosity_Elastic_(Boger)_Fluids]).
carreau_fluid (See: [http://en.wikipedia.org/wiki/Carreau_fluid]).
casson_fluid (industry standard model for molten milk chocolate)
compressible_fluid
cross_fluid (See: [http://en.wikipedia.org/wiki/Cross_fluid]).
dilatant_fluid (shear thickening fluid or STF)
first_order_fluid
herschel_bulkley_fluid (See: [http://en.wikipedia.org/wiki/Herschel-Bulkley_fluid]).
incompressible_fluid
kelvin_voigt_fluid (a linear viscoelastic model; same as "kelvin_material" ?? ######)
maxwell_fluid (a linear viscoelastic model. See: [http://en.wikipedia.org/wiki/Maxwell_material Maxwell material].)
newtonian_fluid (linear relation between shear stress and strain rate that goes through origin)
nonnewtonian_fluid
oldroyd_fluid (a linear viscoeleastic model; see [http://en.wikipedia.org/wiki/Oldroyd-B_model Oldroyd-B model].
power_law_fluid (generalized Newtonian, Ostward-de Waele)
pseudoplastic_fluid (shear thinning)
quemada_fluid (Used to model blood. See: [http://en.wikipedia.org/wiki/Hemorheology Hemorheology].)
rheopectic_fluid
second_order_fluid
super_fluid (See: [http://en.wikipedia.org/wiki/Superfluid Superfluid]).
thixotropic_fluid (See: [http://en.wikipedia.org/wiki/Thixotropy Thixotropy].)
viscoelastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastic].)
viscoplastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoplastic Viscoplastic].)

Note: Use "inviscid_flow" vs. "inviscid_fluid" and "viscous_flow" vs. "viscous_fluid".

 


== {{ Bar Heading| text=Material-Type Assumptions}} ==
:
* These names all end in "_material".

* There is sometimes a blurred semantic distinction between a "material model" (e.g. Arruda-Boyce model) and just a "material'. There are many named models (see separate section) for mathematical models of materials.

* Some types of materials can exist as either a solid or a fluid, and an extra assumption tag should be used to specify if one or the other is assumed.

* "Material" is used as a generic term. See: [http://en.wikipedia.org/wiki/Materials_science Materials science].)

amorphous_material (e.g. gel, glass; also noncrystalline_material. See: [http://en.wikipedia.org/wiki/Amorphous_solid].)
auxetic_material (See: [http://en.wikipedia.org/wiki/Auxetics Auxetics].)
bio_material (See: [http://en.wikipedia.org/wiki/Biomaterial Biomaterial].)
cauchy_elastic_material (same as simple elastic material)
ceramic_material (See: [http://en.wikipedia.org/wiki/Ceramic_materials Ceramic materials].)
composite_material (See: [http://en.wikipedia.org/wiki/Composite_materials Composite materials].)
compressible_material
crystalline_material (or solid?)
elastic_material (See: [http://en.wikipedia.org/wiki/Elasticity_(physics) Elasticity].)
elastoplastic_material
elastoviscoplastic_material (or solid?)
glass_material (amorphous solid that exhibits a glass transition. See: [http://en.wikipedia.org/wiki/Glass Glass].)
homogeneous_material
hyperelastic_material (See: [http://en.wikipedia.org/wiki/Hyperelastic_material Hyperelastic material]. Also called green elastic material and special case of cauchy elastic material.)
hypoelastic_material (See: [http://en.wikipedia.org/wiki/Hypoelastic_material Hypoelastic material]).
incompressible_material
isotropic_material
kelvin_voigt_material (See: [http://en.wikipedia.org/wiki/Kelvin-Voigt_material Kelvin-Voigt Material].)
linear_elastic_material
maxwell_material (See: [http://en.wikipedia.org/wiki/Maxwell_material].)
mohr_coulomb_material (See: [http://en.wikipedia.org/wiki/Mohr-Coulomb_theory Mohr-Coulomb theory]. Model or material type?)
nonlinear_elastic_material
plastic_material (See: [http://en.wikipedia.org/wiki/Plastic Plastic]. Compare to polymeric material.)
polymeric_material (See: [http://en.wikipedia.org/wiki/Polymer Polymer].)
semicrystalline_material
solid_material (for cases where material may be fluid or solid)
thermoelastic_material
viscoelastic_material (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastisticity].)
viscoplastic_material (See: [http://en.wikipedia.org/wiki/Viscoplasticity Viscoplasticity].)

 


== {{ Bar Heading| text=Function-Type Assumptions}} ==
:
* These names all end in "_function".
* See Geometry and Shape Assumptions.

analytic_function
bijective_function
chebyshev_polynomial_function
circle_function
complex_valued_function
constant_function
continuous_function
cosine_function
cumulative_distribution_function
daubechies_d2_wavelet_function (actually a whole family, with d2, d4, ..., d20)
decreasing_function
differentiable_function
differentiable_twice_function
dirac_delta_function
discontinuous_function
ellipse_function
exponential_function
gamma_function
gaussian_function
golden_spiral_function
haar_wavelet_function
harmonic_function
hermite_polynomial_function
hermitian_wavelet_function
holomorphic_function (very similar to "analytic_function")
hyperbola_function
identity_function
increasing_function
injective_function
inverse_function
linear_function
log_function
log_spiral_function (See: [http://en.wikipedia.org/wiki/Logarithmic_spiral Log spiral].)
logit_function (See: [http://en.wikipedia.org/wiki/Logit Logit function].)
monotonic_function
negative_function
nondecreasing_function (distinct from "increasing_function")
nonnegative_function
parabola_function (same as "quadratic_function")
periodic_function
polynomial_function
positive_function
power_law_function
probability_density_function
probit_function (See: [http://en.wikipedia.org/wiki/Probit Probit function].)
real_valued_function
ricker_wavelet_function ("mexican hat wavelet")
sawtooth_wave_function
sine_function
sqrt_function
square_wave_function (See: [http://en.wikipedia.org/wiki/Square_wave square wave].)
step_function (See: [http://en.wikipedia.org/wiki/Heaviside_step_function Heaviside step function].)
tanh_function
triangle_wave_function

See: [http://en.wikipedia.org/wiki/List_of_mathematical_functions List of mathematical functions (Wikipedia)].

Note that "multivalued_function" is a misnomer. See: [http://en.wikipedia.org/wiki/Multiple-valued_function multivalued function].)

* These are already included with Probability Distributions
beta_density_function
gompertz_function

* We could have a similar section for '''surfaces'''.
continuous_surface
differentiable_surface
differentiable_twice_surface

 


== {{ Bar Heading| text=Geometric Assumptions}} ==
:
* Most of these names end in "_shaped".
* The polygons here are assumed to be regular polygons. If they aren't, insert the adjective "irregular".
* See: [http://en.wikipedia.org/wiki/Geometry Geometry].

circle_shaped
cone_shaped
cube_shaped
cylinder_shaped
ellipse_shaped
ellipsoid_shaped (e.g. for earth)
half_plane
hexagon_shaped
hyperbola_shaped
octagon_shaped
parabola_shaped
pentagon_shaped
prism_shaped
rectangle_shaped
rhombus_shaped
semicircle_shaped (e.g. for a channel_cross_section)
sphere_shaped
square_pyramid_shaped
square_shaped
trapezoid_shaped (e.g. for a channel_cross_section)
triangular_pyramid_shaped

concave
concave_upward (long profiles)
convex

 


== {{ Bar Heading| text=Exclusions}} ==
:
* These are objects or effects that are neglected or excluded from consideration in a model.
* Only relevant/important exclusions should be reported.
* Most of these names start with "no_".
:
no_aerosols (1 in CF)
no_anthropogenic_effects
no_antrhopogenic_land_use_change (###### 1 in CF; excluding_anthropogenic_land_use_change)
no_baseflow (hydrology) (1 in CF; excluding_baseflow)
no_bioturbation
no_clouds (1 in CF)
no distributaries
no_friction
no_interception (hydrology)
no_litter (on forest floor) (1 in CF; excluding_litter)
no_longwave-radiation
no_macropores
no_overbank_flow
no_radial_flow (explained and duplicated in "Flow type assumptions")
no_rainfall
no_relativistic_effects
no_resistance
no_shadowing
no_shortwave-radiation
no_slipping
no_sloped-terrain
no_swirl_flow (explained and duplicated in "Flow type assumptions")
no_snow (1 in CF)
no_snowfall
no_tides (2 in CF)
no_turbulence
no_vegetation
## no_viscosity (use inviscid_flow)
no_waves

 


== {{ Bar Heading| text=Named Model-Type Assumptions (by Domain)}} ==
:
* These names all end in "_model".

'''Aerodynamics Models'''
clark_x_airfoil_model
clark_y_airfoil_model
clark_z_airfoil_model
eppler_1200_airfoil_model
joukowski_airfoil_model

'''Agent-Based Models'''
agent_based_model (See: [http://en.wikipedia.org/wiki/Agent_based_model Agent-based model].)
reynolds_flocking_model
schelling_segregation_model [http://web.mit.edu/rajsingh/www/lab/alife/schelling.html Schelling segregation model]

'''Atmosphere and Radiation Models'''
boussinesq_approximation (not in CF, but see for_*)
brutsaert_saturated_vapor_pressure_model
clear_sky (23 in CF)
deep_snow (1 in CF)
horizontal_plane_topography (for clear-sky radiation calculation, not in CF)
(OR zero_slope_terrain, OR no_sloped_terrain OR nonsloped_terrain ???
rigid_lid (in CF; always related to boussinesq approximation ??)
satterlund_saturated_vapor_pressure_model
sea_level_for_geoid (4 in CF)
standard_pressure (not in CF)
standard_temperature (not in CF)

'''Chemistry Models'''
atomic_shell_model
bohr_model
nuclear_shell_model (See: [http://en.wikipedia.org/wiki/Nuclear_shell_model nuclear shell model].)
rutherford_model
valence_bond_model
vespr_model (See: [http://en.wikipedia.org/wiki/VSEPR_Theory VESPR theory].)

'''Cosmological Models'''
baum_frampton_model (a cyclic model)
big_bang_model (See: [http://en.wikipedia.org/wiki/Big_bang Big bang]).
big_bounce_model
big_crunch_model
conformal_cyclic_model
cyclic_model
dark_energy_model (and dark_mass_model ?)
lambda_cdm_model (standard model of Big Bang cosmology)
steinhardt_turok_model (a cyclic model)

'''Earthquake Models'''
rough_fault_model
slider_block_model
spring_block_seismic_model
travelling_wave_model (include the word "earthquake"? ####)

'''Ecological Models'''
exponential_growth_model
food_web_model [http://en.wikipedia.org/wiki/Food_web Food web]
kolmogorov_predator_prey_model
logistic_growth_model
lotka_volterra_model [http://en.wikipedia.org/wiki/Predator-prey_interaction Lotka-Volterra]
natural_selection_model [http://en.wikipedia.org/wiki/Natural_selection Natural selection]
population_growth_model
richards_growth_model
trophic_cascade_model [http://en.wikipedia.org/wiki/Trophic_cascade Trophic cascade]

'''Fluid Dynamics Models'''
albertson_2d_turbulent_jet_model
batchelor_vortex_model
burgers_vortex_model
couette_flow_model
free_surface_vortex_model
free_vortex_model (irrotational, velocity proportional to 1/r)
goertler_2d_turbulent_jet_model
hill_spherical_vortex_model
horseshoe_vortex_model
lamb_chaplygin_dipole_vortex_model
lamb_oseen_vortex_model
peckham_2d_turbulent_jet_model
poiseuille_flow_model
rankine_vortex_model
rigid_body_vortex_model (velocity proportional to r)
taylor_couette_flow_model
taylor_dean_flow_model
taylor_green_vortex_model
tollmien_2d_turbulent_jet_model
trailing_vortex_model (or wing_tip_vortex_model)
turbulent_jet_model
vortex_ring_model

'''General Physics Models'''
double_pendulum_model (See: [http://en.wikipedia.org/wiki/Double_pendulum Double pendulum].)
foucault_pendulum_model (See: [http://en.wikipedia.org/wiki/Foucalt_Pendulum Foucault Pendulum].)
harmonic_oscillator_model
quantum_harmonic_oscillator_model
simple_pendulum_model (harmonic oscillator ? gravity pendulum?)
standard_particle_physics_model
vibrating_string_model

'''Geodynamics Models'''
:
:

'''Hydrology: Channelized Flow Models'''
d8_surface_flow_model
diffusive_wave_model ####
d_infinity_surface_flow_model ####
dynamic_wave_model
hydraulic_geometry_at_a_station_model
hydraulic_geometry_downstream_model #### (Leopold et al.)
kinematic_wave_model
law_of_the_wall_flow_resistance_model ##### ???
manning_flow_resistance_model ##### ???
mass_flux_flow_model
muskingum_flow_routing_model (routing flow through a channel network)
rational_regime_model

'''Hydrology: Evaporation (and sometimes Transpiration) Process Models'''
(See: [http://library.wrds.uwyo.edu/wrp/87-06/ch-04.html Methods for estimating ET].)
asce_standardized_evaporation_model (in CUAHSI HIS HydroModeler)
blaney_criddle_evaporation_model
debruin_evaporation_model (lakes and ponds)
energy_balance_evaporation_model
hargreaves_evaporation_model (remove the "s" in hargreaves ??)
jensen_haise_evaporation_model
kohler_nordenson_fox_evaporation_model (lakes and reservoirs)
kohler_parmele_evaporation_model
penman_evaporation_model
penman_monteith_evaporation_model
priestley_taylor_evaporation_model
shuttleworth_evaporation_model (a modified penman model)
stewart_rouse_evaporation_model (lakes and ponds)
thornthwaite_water_balance_model ########

'''Hydrology: Ground Water and Infiltration Modeling Assumptions'''
(also see dupuit_forschheimer in Modeling Methods.)
brooks_corey_soil_model ? ####
confined_aquifer ####
dupuit_assumption
homogeneous_medium (separate from isotropic ??)
horizontal_flowlines (and vertical equipotential lines)
hydraulic_gradient_equals_free_surface_gradient
hydraulic_gradient_equals_land_surface_gradient
hydraulic_gradient_invariant_with_depth
hydrostatic_pressure_head
impermeable_horizontal_base (or impermeable_boundary_at_base)
impermeable_lower_boundary (or impermeable_base)
isotropic_medium
steady_state_recharge ???
transitional_brooks_corey_soil_model ? ####
unconfined_aquifer ####
van_genuchten_soil_model ? ####

'''Hydrology: Infiltration Process Models'''
beven_infiltration_model (assumes Ks decays exponentially)
green_ampt_infiltration_model
horton_infiltration_model
infiltrated_depth_approximation (not in CF) (Used by Green-Ampt and Smith-Parlange)
(or infiltrability_depth_approximation)
philip_infiltration_model
richards_1d_infiltration_model
richards_3d_infiltration_model
scs_curve_number_infiltration_model (remove "curve number"?)
smith_parlange_infiltration_model

'''Hydrology: Snowmelt Models'''
degree_day_snowmelt_model
energy_balance_snowmelt_model

'''Hydrology: Soil Models'''
brooks_corey_soil_model
darcy_soil_model ?###### See Equations, Laws, Etc.
transitional_brooks_corey_soil_model
van_genuchten_soil_model

'''Hydrology: Surface Water Modeling Assumptions'''
bankfull_flow (or maximum inbank flow)
channel_width_less_than_model_cell_width
convergent_topography
convergent_or_divergent_topography ###### ?
d8_flow_between_cells
d_infinity_flow_between_cells
diffusive_wave
dynamic_wave
hydrologically_sound (applied to a DEM)
impermeable_surface ???
inbank_flow (an accepted term; contrast with overbank and bankfull flow)
kinematic_wave (hydraulic_slope_equals_channel_slope)
law_of_the_wall (also listed with equations)
liquid_water_equivalent (used to clarify a quantity like precipitation_rate)
manning_equation (also listed with equations)
mass_flux_method_flow_between_cells
overbank_flow
overland_flow
prismatic_channels
sheet_flow
spatially_uniform_rainfall
#### instantaneous_unit_hydrograph idea ???

'''Illumination and Shading Models'''
See: [http://en.wikipedia.org/wiki/List_of_common_shading_algorithms List of common shading algorithms].
blinn_phong_illumination_model
cook_torrance_illumination_model
flat_shading_model
gouraud_shading_model
lambert_illumination_model (lambert vs. lambertian)
minnaert_illumination_model
oren_nayer_illumination_model
phong_illumination_model
phong_shading_model
ward_anisotropic_illumination_model

'''Infiltration Models (Ventilation Models)'''
lbl_infiltration_model
sherman_grimsrud_infiltration_model

'''Nonlinear Science Models'''
aperiodic_tiling_model (See: [http://en.wikipedia.org/wiki/Aperiodic_tiling Aperiodic tiling].)
bond_percolation_model (what type of lattice ??)
cellular_automata_model
diffusion_limited_aggregation_model
dimer_model (and "double_dimer_model" ?)
ehrenfest_urn_model
fisher_droplet_model
interacting_particle_system_model
ising_model
lattice_gas_model (includes: lattice_gas_automata_model and lattice_boltzmann_model. See: [http://en.wikipedia.org/wiki/Lattice_gas_automaton Lattice gas automaton].)
logistic_map_model
penrose_tiling_model
potts_model (See: [http://en.wikipedia.org/wiki/Potts_model Potts model].)
sandpile_model (Per Bak, self-organized criticality)
self_similar_tree_model
site_percolation_model (what type of lattice ??)
voter_model

'''Ocean Models'''
deep_water_wave
edge_wave
fully_developed_sea
kelvin_wave (coastal or equatorial)
passive_scalar (e.g. temperature and salinity, perhaps suspended sediment)
### per_unit_length_of_wave_crest
rossby_wave
shallow_water_wave
shore_parallel_contours (not in CF)
stokes_wave

'''Sediment Transport Models'''
bagnold_sediment_transport_model (distinguish total load and bedload ####)
detachment_limited_sediment_transport
einstein_sediment_transport_model
komar_longshore_sediment_transport_model ####
meier_peter_mueller_sediment_transport_model
supply_limited_sediment_transport

'''Thermodynamics Models'''
black_body_model (See: [http://en.wikipedia.org/wiki/Black_body Black body].)
carnot_heat_engine_model (See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine]).
gray_body_model
white_body_model

'''Turbulence and Turbulence Closure Models'''
See: [http://en.wikipedia.org/wiki/Turbulence_modeling Turbulence modeling].
detached_eddy_simulation_model (DES)
direct_numerical_simulation_model (DNS) (Navier-Stokes solved without a turbulence model)
eddy_viscosity_model (due to Boussinesq, 1887)
k_epsilon_model (due to Jones and Launder)
k_omega_model (due to Kolmogorov ??)
kolmogorov_statistical_turbulence_model
large_eddy_simulation_model (LES) ?? #####
menter_shear_stress_transport_model
prandtl_mixing_length_model (due to Prandtl)
reynolds_averaged_navier_stokes_model (or reynolds_shear_stress_model)
smagorinsky_model (due to Smagorinsky, 1964; for sub-grid scale eddy viscosity)
spalart_allmaras_model

'''Water Wave Models'''
airy_wave_model [http://en.wikipedia.org/wiki/Airy_wave_theory Airy waves]
capillary_wave_model (type of wave vs. model for waves?)
cnoidal_wave_model [http://en.wikipedia.org/wiki/Cnoidal_wave Cnoidal waves]
kelvin_wave_model [http://en.wikipedia.org/wiki/Kelvin_wave]
korteweg_devries_solitary_wave_model
russell_solitary_wave_model
solitary_wave_model
stokes_wave_model
tsunami_wave_model

:
'''Models Not Yet Grouped'''
general_relativity_model
hagen_poiseuille (pressure drop in a pipe; laminar, viscous, incompressible)
harmonic_function (solution to Laplace equation)
hydraulic_jump
inclined_plane
power_law ####
special_relativity_model
unnamed_empirical_law ####
VSEPR (to compute molecular geometry)
boussinesq_buoyancy_approximation
dispersion_relation (could be linear)
kramers_kronig_relations

 


== {{ Bar Heading| text=Thermodynamic Process Assumptions}} ==
:
* These names all end in "_process". See: [http://en.wikipedia.org/wiki/Thermodynamic_process Wikipedia: Thermodynamic process] and links therein.

adiabatic_process (See: [http://en.wikipedia.org/wiki/Adiabatic_process Adiabatic]).
cyclic_process
diabatic_process
endoreversible_process
endothermic_process (better as adjective? absorbs energy)
exothermic_process (better as adjective? releases energy)
irreversible_process
isentropic_process (also called "reversible" ?; See: [http://en.wikipedia.org/wiki/Isentropic_process Isentropic]).
isenthalpic_process (also called "isoenthalpic"; See: [http://en.wikipedia.org/wiki/Isenthalpic Isenthalpic]).
isobaric_process
isocaloric_process
isochoric_process
isothermal_process
polytropic_process
quasistatic_process (reversible implies quasistatic, but not conversely)
reversible_process
thermal_equilibrium #### (See "black_body_model".) (See: [http://en.wikipedia.org/wiki/Thermal_equilibrium Thermal equilibrium]).

 


== {{ Bar Heading| text=Stochastic Model Assumptions}} ==
:
* Many of these end with the word "_process", which is part of the standard terminology. Many others end with "_distribution".

* See [http://en.wikipedia.org/wiki/Stochastic_process Wikipedia: Stochastic process] and [http://en.wikipedia.org/wiki/List_of_stochastic_processes_topics List of Stochastic Process Topics].

autoregressive
bernoulli_process
bessel_process
birth_death_process
blue_noise_process
branching_process
brownian_bridge_process
brownian_motion_process
buffon_needle_process
cauchy_process
chinese_restaurant_process
colored_noise_process
compound_poisson_process
contact_process
continuous_process
continuous_time_process
counting_process
coverage_process
cox_point_process
diffusion_process
dirichlet_process
discrete_process
discrete_time_process
ergodic_process
feller_process
fractional_brownian_motion_process
galton_watson_process
gaussian_white_noise_process
geometric_brownian_motion_process
grey_noise_process
homogeneous
hunt_process
independent_increments
#### independent_and_identically_distributed (use both)
infinitely_divisible_process
inhomogeneous_poisson_process
ito_diffusion_process
jump_diffusion_process
jump_process
levy_process
linear_least_squares_regression
local_time_process
markov_process
martingale_process
mckean_vlasov_process
moran_process
moving_average
negative (process?)
nonlinear_least_squares_regression
nonnegative (process?)
nonstationary_process
ornstein_uhlenbeck_process
pink_noise_process
point_process
poisson_event_process
poisson_line_process
poisson_point_process
poisson_polygon_process
poisson_process
polya_tree_process
positive (process?)
power_law_noise_process
pure_jump_process
random_multiplicative_cascade_process (is there "additive", too?)
random_tree_process
random_walk_process (symmetric or unsymmetric)
red_noise_process
renewal_process (generalization of Poisson point process)
risk_process
schramm_loewner_evolution_process (See: [http://en.wikipedia.org/wiki/Stochastic_Loewner_evolution SLE process]).
second_order_stationary_process
self_avoiding_random_walk_process
semi_markov_process
shot_noise_process (e.g. raindrops on a roof)
stable_process
stationary_process
storage_process
telegraph_process
uncorrelated
violet_noise_process
weak_stationarity_of_order_k
white_noise_process
wiener_process

 


== {{ Bar Heading| text=Probability Distributions}} ==
:
* Many of these end with the word "_distribution",
* Also see: [http://en.wikipedia.org/wiki/List_of_probability_distributions List of probability distributions] (Wikipedia).
* Most of these are '''named''' distributions, but some are a '''type''' of distribution (e.g. discrete distribution).
:
arcsine_distribution (See: [http://en.wikipedia.org/wiki/Arcsine_distribution Arcsine distribution].)
bates_distribution (See: [http://en.wikipedia.org/wiki/Bates_distribution Bates distribution].)
benford_distribution (See: [http://en.wikipedia.org/wiki/Benford%27s_law Benford's law].)
bernoulli_distribution (See: [http://en.wikipedia.org/wiki/Bernoulli_distribution Bernoulli distribution].)
beta_distribution (See: [http://en.wikipedia.org/wiki/Beta_distribution Beta distribution].)
beta-binomial_distribution (See: [http://en.wikipedia.org/wiki/Beta-binomial_distribution Beta-binomial distribution].)
beta-prime_distribution (See: [https://en.wikipedia.org/wiki/Beta_prime_distribution Beta prime distribution].)
bimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
binomial_distribution (See: [http://en.wikipedia.org/wiki/Binomial_distribution Binomial distribution].)
boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Boltzmann_distribution Boltzmann distribution].)
borel_distribution (See: [http://en.wikipedia.org/wiki/Borel_distribution Borel distribution].)
borel-tanner_distribution
burr_distribution (See: [https://en.wikipedia.org/wiki/Burr_distribution Burr distribution].)
cauchy_distribution (See: [http://en.wikipedia.org/wiki/Cauchy_distribution Cauchy distribution].)
champernowne_distribution (See: [http://en.wikipedia.org/wiki/Champernowne_distribution Champernowne distribution].)
chi-squared_distribution
continuous_distribution
continuous_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(continuous) Uniform distribution (continuous)].)
dagum_distribution (See: [https://en.wikipedia.org/wiki/Dagum_distribution Dagum distribution].)
dirichlet_distribution (See: [https://en.wikipedia.org/wiki/Dirichlet_distribution Dirichlet distribution].)
dirichlet-multinomial_distribution (See: [http://en.wikipedia.org/wiki/Dirichlet-multinomial_distribution Dirichlet-multinomial distribution].)
discrete_distribution
discrete_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(discrete) Uniform distribution (discrete)].)
elliptical_distribution (See: [http://en.wikipedia.org/wiki/Elliptical_distribution Elliptical distribution].)
exponential_distribution (See: [http://en.wikipedia.org/wiki/Exponential_distribution Exponential distribution].)
first-contact_distribution (See: [http://en.wikipedia.org/wiki/Spherical_contact_distribution_function Spherical contact distribution].)
frechet_distribution (See: [http://en.wikipedia.org/wiki/Fréchet_distribution Frechet distribution].)
gamma_distribution (See: [http://en.wikipedia.org/wiki/Gamma_distribution Gamma distribution].)
gaussian_distribution (See: [https://en.wikipedia.org/wiki/Normal_distribution Normal distribution].)
generalized_extreme_value_distribution (See: [http://en.wikipedia.org/wiki/Generalized_extreme_value_distribution GEV distribution].)
generalized_pareto_distribution
geometric_distribution (See: [http://en.wikipedia.org/wiki/Geometric_distribution Geometric distribution].)
geometric-stable_distribution (See: [http://en.wikipedia.org/wiki/Geometric_stable_distribution Geometric stable distribution].)
gompertz_distribution (See: [http://en.wikipedia.org/wiki/Gompertz_function Gompertz function].)
gumbel_distribution (See: [http://en.wikipedia.org/wiki/Gumbel_distribution Gumbel distribution].)
half-normal_distribution (See: [http://en.wikipedia.org/wiki/Half-normal_distribution Half-normal distribution].)
hitting-time_distribution (See: [http://en.wikipedia.org/wiki/Hitting_time Hitting time].)
holtsmark_distribution (See: [http://en.wikipedia.org/wiki/Holtsmark_distribution Holtsmark distribution].)
hyperbolic_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_distribution Hyperbolic distribution].)
hyperbolic-secant_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_secant_distribution Hyperbolic secant distribution].)
hypergeometric_distribution (See: [http://en.wikipedia.org/wiki/Hypergeometric_distribution Hypergeometric distribution].)
identically_distributed ####
independently_distributed #####
inverse-gamma_distribution (See: [http://en.wikipedia.org/wiki/Inverse-gamma_distribution Inverse-gamma distribution].)
inverse-gaussian_distribution (See: [http://en.wikipedia.org/wiki/Inverse_Gaussian_distribution Inverse Gaussian distribution].)
irwin-hall_distribution (See: [http://en.wikipedia.org/wiki/Irwin–Hall_distribution Irwin-Hall distribution].)
joint-probability_distribution (See: [http://en.wikipedia.org/wiki/Joint_probability_distribution Joint probability distribution].)
kent_distribution (See: [http://en.wikipedia.org/wiki/Kent_distribution Kent distribution].)
landau_distribution (See: [http://en.wikipedia.org/wiki/Landau_distribution Landau distribution].)
laplace_distribution (See: [http://en.wikipedia.org/wiki/Laplace_distribution Laplace distribution].)
levy_distribution (See: [http://en.wikipedia.org/wiki/Lévy_distribution Levy distribution].)
log-cauchy_distribution (See: [http://en.wikipedia.org/wiki/Log-Cauchy_distribution Log-Cauchy distribution].)
log-logistic_distribution (See: [http://en.wikipedia.org/wiki/Log-logistic_distribution Log-logistic distribution].)
log-normal_distribution (See: [http://en.wikipedia.org/wiki/Log-normal_distribution Log-normal distribution].)
log-poisson_distribution
log-symmetric_distribution
logarithmic_distribution (See: [http://en.wikipedia.org/wiki/Logarithmic_distribution Logarithmic distribution].)
logistic_distribution (See: [http://en.wikipedia.org/wiki/Logistic_distribution Logistic distribution].)
logit-normal_distribution (See: [http://en.wikipedia.org/wiki/Logit-normal_distribution Logit-normal distribution].)
lomax_distribution (See: [https://en.wikipedia.org/wiki/Lomax_distribution Lomax distribution].)
maximum_entropy_probability_distribution (See: [http://en.wikipedia.org/wiki/Maximum_entropy_probability_distribution Max entropy pdf].)
maxwell-boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Maxwell–Boltzmann_distribution Maxwell-Boltzmann distribution].)
mixture_distribution (See: [http://en.wikipedia.org/wiki/Mixture_distribution Mixture distribution].)
multimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
multinomial_distribution (See: [http://en.wikipedia.org/wiki/Multinomial_distribution Multinomial distribution].)
nakagami_distribution (See: [http://en.wikipedia.org/wiki/Nakagami_distribution Nakagami distribution].)
negative-binomial_distribution (See: [http://en.wikipedia.org/wiki/Negative_binomial_distribution Negative binomial distribution].)
parabolic-fractal_distribution (See: [http://en.wikipedia.org/wiki/Parabolic_fractal_distribution Parabolic fractal distribution].)
pareto_distribution (See: [http://en.wikipedia.org/wiki/Pareto_distribution Pareto distribution].)
pascal_distribution (special case of negative binomial.)
pearson_distribution (See: [http://en.wikipedia.org/wiki/Pearson_distribution Pearson distribution].)
poisson_distribution (See: [http://en.wikipedia.org/wiki/Poisson_distribution Poisson distribution].)
poisson-binomial_distribution (See: [http://en.wikipedia.org/wiki/Poisson_binomial_distribution Poisson binomial distribution].)
polya_distribution (special case of negative binomial)
rademacher_distribution (See: [http://en.wikipedia.org/wiki/Rademacher_distribution Rademacher distribution].)
rayleigh_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_distribution Rayleigh distribution].)
rayleigh-mixture_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_mixture_distribution Rayleigh mixture distribution].)
reciprocal_distribution (See: [http://en.wikipedia.org/wiki/Reciprocal_distribution Reciprocal distribution].)
rice_distribution (See: [http://en.wikipedia.org/wiki/Rice_distribution Rice distribution].)
skellam_distribution (See: [http://en.wikipedia.org/wiki/Skellam_distribution Skellam distribution].)
skew-normal_distribution (See: [http://en.wikipedia.org/wiki/Skew_normal_distribution Skew normal distribution].)
slash_distribution (See: [http://en.wikipedia.org/wiki/Slash_distribution Slash distribution].)
stable_distribution (See: [http://en.wikipedia.org/wiki/Stable_distribution Stable distribution].)
student-t_distribution (See: [http://en.wikipedia.org/wiki/Student%27s_t-distribution Student's t-distribution].)
symmetric_distribution (See: [http://en.wikipedia.org/wiki/Symmetric_probability_distribution Symmetric distribution].)
tracy-widom_distribution (See: [http://en.wikipedia.org/wiki/Tracy–Widom_distribution Tracy-Widom distribution].)
triangular_distribution (See: [http://en.wikipedia.org/wiki/Triangular_distribution Triangular distribution].)
truncated_distribution (See: [http://en.wikipedia.org/wiki/Truncated_distribution Truncated distribution].)
tukey-lambda_distribution (See: [http://en.wikipedia.org/wiki/Tukey_lambda_distribution Tukey lambda distribution].)
u-quadratic_distribution (See: [http://en.wikipedia.org/wiki/U-quadratic_distribution U-quadratic distribution].)
unimodal_distribution
voigt_distribution (See: [http://en.wikipedia.org/wiki/Voigt_profile Voigt profile].)
von-mises_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises_distribution von Mises distribution].)
von-mises-fisher_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises–Fisher_distribution von Mises-Fisher distribution].)
weibull_distribution (See: [http://en.wikipedia.org/wiki/Weibull_distribution Weibull distribution].)
yule-simon_distribution (See: [http://en.wikipedia.org/wiki/Yule–Simon_distribution Yule-Simon distribution].)
zeta_distribution (See: [http://en.wikipedia.org/wiki/Zeta_distribution Zeta distribution].)
zipf_distribution (See: [http://en.wikipedia.org/wiki/Zipf%27s_law Zipf's law].)

 


== {{ Bar Heading| text=Statistical Operation Assumptions}} ==
:
* Perhaps this should be generalized to something like "Data Transformation Assumptions"?
* These names currently all end with "averaged".
* For ones that start with a unit of time, one of those units is assumed. A number can be inserted in front, when necessary, as in "two_day_averaged".

cell_averaged
day_averaged
depth_averaged
domain_averaged
hour_averaged
interval_averaged
month_averaged
population_averaged
sample_averaged
section_averaged
time_averaged
vertically_averaged
watershed_averaged
year_averaged

 


== {{ Bar Heading| text=Mathematical Assumptions}} ==
:
algebraic (equation)
bijection
bounded (set)
closed (set, curve)
compact (set)
complex-valued
conformal
constant_coefficients (equation or polynomial)
continuous
continuum (continuum_hypothesis ?)
contraction_mapping
countably_infinite
degenerate
differentiable
differentiable_twice
differentiable_three_times
differential (equation)
discontinuous
equal_mixed_partials
finite
fixed_point
ill-posed
infinite
injective
integer-valued
invertible
irrational
jordan_curve
linear
multiple_valued_function ### (misnomer)
negative
nonlinear
nonnegative
orthogonal
permutation
positive
projection
rational
real-valued
spatially_uniform
superposition
symmetric
time_space_substitution
uncountably_infinite
uniform
weak_solution
well-posed

 


== {{ Bar Heading| text=Numerical Grid Assumptions}} ==
:
* Most of these end with the word '''grid'''.
* The word "grid" is used to include the word "mesh".
:
adaptive_grid
arakawa_a_grid (unstaggered)
arakawa_b_grid (staggered)
arakawa_c_grid (staggered)
arakawa_d_grid (staggered, rotated 90 degrees)
arakawa_e_grid (staggered, rotated 45 degrees)
arakawa_u_component (attached to an input var)
arakawa_v_component (attached to an input var)
arakawa_w_component (attached to an input var)
block_structured_grid
boundary-fitted_grid (also called "body-fitted")
delaunay_triangle_grid
hexagon_grid
orthogonal_curvilinear_grid
rectilinear_grid
square_grid
staggered_grid (###### already in arakawa system ??)
structured_grid
triangle_grid
uniform_grid
unstructured_grid
voronoi_polygon_grid

 


== {{ Bar Heading| text=Numerical Method Assumptions}} ==
:
* These are used to describe the numerical method that a model uses to solve the equations it uses to compute variables of interest. The equations could be ODEs, PDEs, algebraic equations (e.g. root finding), etc. We probably don't need separate assumption names like "ode" and "pde" because that is implied by the equation name. See Equations, Laws and Principles for a standardized list of equation names.
* Most of these names end with "_method", "_scheme" or "_grid".
* See: [http://en.wikipedia.org/wiki/List_of_Runge–Kutta_methods List of Runge-Kutta methods].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_ordinary_differential_equations Numerical methods for ODEs].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_partial_differential_equations Numerical methods for PDEs].
:
a-stable_method
absolutely-stable_method
adams-bashforth_method
adaptive_mesh_refinement_method (See: [http://en.wikipedia.org/wiki/Adaptive_mesh_refinement Adaptive mesh refinement].)
adaptive_stepsize_method (See: [http://en.wikipedia.org/wiki/Adaptive_stepsize Adaptive stepsize].)
adjoint_state_method (See: [http://en.wikipedia.org/wiki/Adjoint_state_method Adjoint state method].)
analytic_element_method (See: [http://en.wikipedia.org/wiki/Analytic_element_method: Analytic element method]).
backward_difference_scheme
backward_euler_method (See: [http://en.wikipedia.org/wiki/Backward_Euler_method Backward Euler method].)
boundary_element_method (See: [http://en.wikipedia.org/wiki/Boundary_element_method Boundary element method].)
central_difference_scheme (See: [http://en.wikipedia.org/wiki/Central_differencing_scheme Central differencing scheme].)
characteristics_method (known as "method of characteristics")
collocation_method (See: [http://en.wikipedia.org/wiki/Collocation_method Collocation method].)
conditionally_stable_method
conjugate_gradient_method (See: [http://en.wikipedia.org/wiki/Conjugate_gradient_method Conjugate gradient method].)
consistent_method
convergent_method
crank-nicolson_method (See: [http://en.wikipedia.org/wiki/Crank–Nicolson_method Crank-Nicolson method].)
direct_numerical_solution
discrete_element_method (See: [http://en.wikipedia.org/wiki/Discrete_element_method Discrete element method].)
discrete_event_simulation (See: [http://en.wikipedia.org/wiki/Discrete_event_simulation Discrete event simulation].)
dynamic_relaxation_method (See: [http://en.wikipedia.org/wiki/Dynamic_relaxation Dynamic relaxation].)
euler_method (See: [http://en.wikipedia.org/wiki/Euler_method Euler method].) (distinguish between "forward" and "backward" with a prefix?)
explicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
fast_marching_method (See: [http://en.wikipedia.org/wiki/Fast_marching_method Fast marching method], a type of level_set_method.)
finite_difference_method (See: [http://en.wikipedia.org/wiki/Finite_difference_method Finite difference method].)
finite_element_method (See: [http://en.wikipedia.org/wiki/Finite_element_method Finite element method].)
finite_volume_method (See: [http://en.wikipedia.org/wiki/Finite_volume_method Finite volume method].)
first_order_accurate
five-point_stencil_method (See: [http://en.wikipedia.org/wiki/Five-point_stencil Five-point stencil].)
forward_difference_scheme
forward_time_centered_space_scheme (FTCS scheme)
galerkin_method (See: [http://en.wikipedia.org/wiki/Galerkin_method Galerkin method].)
gauss-legendre_method (See: [http://en.wikipedia.org/wiki/Gauss–Legendre_method Gauss-Legendre method].)
gauss-seidel_method (See: [http://en.wikipedia.org/wiki/Gauss–Seidel_method Gauss-Seidel method].)
halley_method (See: [http://en.wikipedia.org/wiki/Halley%27s_method Halley's method].)
heun_method (See: [http://en.wikipedia.org/wiki/Heun%27s_method Heun's method].)
implicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
interior_point_method (See: [http://en.wikipedia.org/wiki/Interior_point_method Interior point method].)
iterative_method (See: [http://en.wikipedia.org/wiki/Iterative_method Iterative method].)
l-stable_method (See: [http://en.wikipedia.org/wiki/L-stability L-stability].)
landweber_iteration_method (See: [http://en.wikipedia.org/wiki/Landweber_iteration Landweber iteration].)
large_eddy_simulation
lattice_boltzmann_method (See: [http://en.wikipedia.org/wiki/Lattice_Boltzmann_methods Lattice Boltzmann methods].)
lax-friedrichs_method (See: [http://en.wikipedia.org/wiki/Lax–Friedrichs_method Lax-Friedrichs method].)
lax-wendroff_method (See: [http://en.wikipedia.org/wiki/Lax–Wendroff_method Lax-Wendroff method].)
leapfrog_method
level_set_method (See: [http://en.wikipedia.org/wiki/Level_set_method Level set method].)
linear_multistep_method (See: [http://en.wikipedia.org/wiki/Linear_multistep_method Linear multistep method].)
maccormack_method (See: [http://en.wikipedia.org/wiki/MacCormack_method MacCormack method].)
meshfree_method (See: [http://en.wikipedia.org/wiki/Meshfree_methods Meshfree method].)
midpoint_method (See: [http://en.wikipedia.org/wiki/Midpoint_method Midpoint method].)
multigrid_method (See: [http://en.wikipedia.org/wiki/Multigrid_method Multigrid method].)
newton_raphson_method (See: [http://en.wikipedia.org/wiki/Newton%27s_method Newton's method]; also see "halley_method".)
numerov_method (See: [http://en.wikipedia.org/wiki/Numerov%27s_method Numerov's method].)
particle-in-cell_method (See: [http://en.wikipedia.org/wiki/Particle-in-cell Particle in cell].)
predictor-corrector_method (See: [http://en.wikipedia.org/wiki/Predictor–corrector_method Predictor-corrector method].)
rayleigh-ritz_method (See: [http://en.wikipedia.org/wiki/Rayleigh–Ritz_method Rayleigh-Ritz method].)
relatively_stable_method
relaxation_method (See: [http://en.wikipedia.org/wiki/Relaxation_(iterative_method) Relaxation (iterative method)].)
runge_kutta_method (See: [http://en.wikipedia.org/wiki/Runge–Kutta_methods Runge-Kutta methods]. There are several distinct types.)
second-order_accurate_method
shooting_method (See: [http://en.wikipedia.org/wiki/Shooting_method Shooting method].)
spectral_method (See: [http://en.wikipedia.org/wiki/Spectral_method Spectral method].)
split-step_method (See: [http://en.wikipedia.org/wiki/Split-step_method Split-step method].)
strongly_stable_method
successive_over_relaxation_method (See: [http://en.wikipedia.org/wiki/Successive_over-relaxation Successive over-relaxation].)
trapezoidal_rule_method (See: [http://en.wikipedia.org/wiki/Trapezoidal_rule_(differential_equations) Trapezoidal rule].)
unconditionally_stable_method
unstable_method
upwind_difference_scheme (See: [http://en.wikipedia.org/wiki/Upwind_differencing_scheme_for_convection Upwind difference scheme].)
upwind_first-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_second-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_third-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
verlet_integration_method (See: [http://en.wikipedia.org/wiki/Verlet_integration Verlet integration].)



== {{ Bar Heading| text=State of Matter Assumptions}} ==
:
* These can be provided when the model involves a substance (object) like water that could be in any of several possible states. See: [http://en.wikipedia.org/wiki/States_of_matter States of matter].
* Note that "liquid_equivalent" can also be inserted in quantity names such as "liquid_equivalent_precipitation_rate" to create a single quantity that can accommodate multiple states of matter.
:
gas_phase
liquid_phase
plasma_phase
solid_phase



== {{ Bar Heading| text=System State Assumptions}} ==
:
asymptotic_equilibrium
bistable
dynamic_equilibrium
equilibrium
ergodic
metastable (See: [http://en.wikipedia.org/wiki/Metastability Metastability]).
stable
static_equilibrium
steady_state
unstable
unsteady_state

 


== {{ Bar Heading| text=CF Convention Standard Name Assumptions}} ==
:
* [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/ '''CF Convention Standard Names'''] often include additional information and assumptions in the name itself. The ones in this section were found in the list of CF Standard Names and the number of occurrences found is listed in parentheses. It is not yet clear how some of these should be captured with standard assumption names.

* Many of these are '''Location Assumptions'''.

above_geoid (3 in CF)
above_land_surface (not in CF)
above_reference_datum (1 in CF)
above_reference_ellipsoid (5 in CF)
above_sea_floor (1 in CF)
above_sea_floor_surface (not in CF)
above_sea_level (1 in CF)
above_threshold (5 in CF)

at_*** (51 in CF)
at_cloud_base (1 in CFFl
at_cloud_top (3 in CF)
at_equilibrium (not in CF)
at_freezing_level (1 in CF)
at_land_surface (not in CF; e.g. air pressure)
at_maximum_upward_derivative (1 in CF)
at_saturation (4 in CF)
at_sea_floor (3 in CF)
at_sea_floor_surface (not in CF; e.g. water pressure)
at_sea_ice_base (8 in CF)
at_sea_level (1 in CF)
at_top_of_*** (3 in CF)
at_bottom_*** (not in CF)

assuming_*** (33 in CF)
assuming_clear_sky (24 in CF)
assuming_deep_snow (1 in CF, for surface_albedo)
assuming_no_aerosol_or_cloud (1 in CF)
assuming_no_snow (1 in CF, for surface_albedo)
assuming_no_tide (2 in CF)
assuming_sea_level_for_geoid (4 in CF)

below_geoid (1 in CF)
below_sea_level (1 in CF)
below_sea_surface (1 in CF)
below_surface (1 in CF)
below_threshold (3 in CF)

between_air_and_sea_water (1 in CF)
between_sea_water_and_air (2 in CF)

due_to_*** (399 in CF)
due_to_all_land_processes (2 in CF)
due_to_convective_cloud (1 in CF)
due_to_diffusion (18 in CF)
due_to_dry_convection (1 in CF)
due_to_dry_deposition (35 in CF)
due_to_dry_troposphere (1 in CF)
due_to_dust_ambient_aerosol (2 in CF)
due_to_emission_from_grazing (in CF)

excluding_anthropogenic_land_use_change (in CF)
excluding_baseflow (in CF)
excluding_litter (in CF)

expressed_as_*** (140 in CF)
expressed_as_carbon (67 in CF)
expressed_as_chlorine (7 in CF)
expressed_as_nitrogen (24 in CF)

for_*** (13 in CF)
for_biomass_growth (1 in CF)
for_biomass_maintenance (1 in CF)
for_boussinesq_approximation (1 in CF)
for_momentum (2 in CF; both "for_momentum_in_air")

per_capita
per_unit_area (already used in CF)
per_unit_length_of_wave_crest
per_unit_mass (already used in CF, and synonym for "specific")
per_unit_time ??
per_unit_width (e.g. discharge_per_unit_width)
(see CF: sea_water_transport_across_line,
and "transport_across_unit_distance")

:
:
:

CSN Assumption Names

2015-11-12T18:09:57Z

Peckhams: /* {{ Bar Heading| text=Probability Distributions}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Assumption Names ''' =
:
* This document provides standardized assumption names or '''descriptors''' for use in Model Coupling Metadata (MCM) files. They are organized into groups which are (for the most part) mutually exclusive and which intend to span the types that are needed to describe a model's underlying physics. They cannot yet be said to be exhaustive but they are illustrative. The ones collected here already illustrate various language patterns that are commonly used to describe assumptions. 

* Note that '''assumption''' is meant to be taken as a broad term that can include things like ''conditions'', ''simplifications'', ''approximations'', ''limitations'', ''conventions'', ''provisos'' and other forms of clarification. 

* CSDMS encourages model developers to include as many <assume> tags in their Model Coupling Metadata (MCM) file as they feel apply to their model or to a particular input or output variable name. XML tag nesting determines the scope of an <assume> tag. For someone familiar with a particular modeling domain, the terms that have been collected here should be easily recognized and understood as part of that domain's standard terminology. 

* Given a collection of models that have Model Coupling Metadata (MCM) files which include a standardized listing of assumptions it will be straightforward to write software that allows the CSDMS modeling framework to automatically check whether two components to be coupled are compatible and alert users to potential problems or mismatches. Reports can also be generated automatically that quantify the ''degree of compatibility''. Similarly, opportunities for valid model coupling can then also be automatically identified.

 

== {{ Bar Heading| text=Boundary Condition Assumptions}} ==
:
* See: [http://en.wikipedia.org/wiki/Boundary_value_problem Boundary value problem] and [http://en.wikipedia.org/wiki/Initial_value_problem Initial value problem]. Initial conditions are also included in this section.
* These all end with "_boundary_condition".

[http://en.wikipedia.org/wiki/Cauchy_boundary_condition cauchy_boundary_condition]
clamped_boundary_condition
constant_pressure_boundary_condition
[http://en.wikipedia.org/wiki/Dirichlet_boundary_condition dirichlet_boundary_condition]
free_surface_boundary_condition
hinged_boundary_condition
moving_boundary_condition
[http://en.wikipedia.org/wiki/Mixed_boundary_condition mixed_boundary_condition]
[http://en.wikipedia.org/wiki/Neumann_boundary_condition neumann_boundary_condition]
natural_boundary_condition
no_normal_flow_boundary_condition
no_slip_boundary_condition
periodic_boundary_condition (same as "wrap-around")
pinned_boundary_condition
[http://en.wikipedia.org/wiki/Robin_boundary_condition robin_boundary_condition]
stefan_boundary_condition (See: [http://en.wikipedia.org/wiki/Stefan_problem Stefan problem].)
tidal_boundary_condition
toroidal_boundary_condition (same as "doubly periodic" ??)

 


== {{ Bar Heading| text=Conserved Quantity Assumptions}} ==
:
* These names all end in "_conserved". See [http://en.wikipedia.org/wiki/Conservation_law Conservation Law] and links therein.
* These names would usually be used within an <object> tag block which would make it clear what is being conserved (e.g. water or sediment).

angular_momentum_conserved
electric_charge_conserved
energy_conserved
linear_momentum_conserved
mass_conserved
momentum_conserved
potential_vorticity_conserved

 


== {{ Bar Heading| text=Coordinate Systems}} ==
:
* These end in "coordinate_system".
* See: [http://en.wikipedia.org/wiki/List_of_common_coordinate_transformations List of common coordinate transformations].
:
bipolar_coordinate_system
boundary-fitted_orthogonal_curvilinear_coordinate_system
cartesian_coordinate_system (same as "rectilinear")
cylindrical_coordinate_system (same as "polar" if 2D)
elliptic_coordinate_system
geographic_coordinate_system
log-polar_coordinate_system
orthogonal_curvilinear_coordinate_system
parabolic_coordinate_system
projected_coordinate_system (i.e. map projections)
right_hand_rule_coordinate_system
spherical_coordinate_system
terrain_following_vertical_coordinate_system (Same as "sigma coordinates"?? See: [http://www.ocean-modeling.org/docs.php?page=s-coordinate S-coordinate models], [http://en.wikipedia.org/wiki/Sigma_coordinate Sigma coordinates].)

 


== {{ Bar Heading| text=Georeferencing Assumptions}} ==
:
* Standard names for projections, ellipsoids and datums are available in the [http://www.epsg-registry.org EPSG Registry].
:
* Standard names for projections, ellipsoids and datums are also used in the [http://trac.osgeo.org/geotiff/ GeoTIFF Spec].
:
:

 


== {{ Bar Heading| text=Sign and Angle Conventions}} ==
:
clockwise_from_east_azimuth_convention
clockwise_from_north_azimuth_convention (all "bearing" angles, e.g. wind "from" angles)
clockwise_from_south_azimuth_convention
counter-clockwise_from_east_azimuth_convention
counter-clockwise_from_x_axis_azimuth_convention (standard math)
x-axis_directed_downwind
x-axis_directed_offshore
y-axis_directed_alongshore
z-axis_directed_downward (positive_downward)
z-axis_directed_upward (positive_upward)
z-axis_normal_to_surface



== {{ Bar Heading| text=Dimensionality Assumptions}} ==
:
* If the "richards_equation" assumption is used for infiltration, keep 1D and 3D out of the assumption name and give one of these with a separate <assume> tag.
* What about things like "1.5-dimensional" models?
:
1d
2d
3d

 

== {{ Bar Heading| text=Equations, Laws and Principles}} ==
:
* An <assume> tag should be provided for each equation that a model (or model component) uses. Most equations have standard names, as shown in the examples below.
:
* These all end in "_equation", "_law" or "_principle", except for the "law of the wall".
:

* See [http://en.wikipedia.org/wiki/Laws_of_science Wikipedia: Laws of Science] and [http://en.wikipedia.org/wiki/List_of_eponymous_laws List of Eponymous Laws].
:
adams_williamson_equation (See: [http://en.wikipedia.org/wiki/Adams–Williamson_equation Adams-Williamson equation].)
ampere_law
archimedes_principle
avogadro_law
beer_lambert_law
bernoulli_principle
biharmonic_equation
biot_savart_law
boltzman_equation
boyle_law
burgers_equation
cauchy_riemann_equations
combined_gas_law
conservation_of_energy_law ###
conservation_of_mass_law ### (same as continuity_equation)
conservation_of_momentum_law ###
coulomb_law
dalton_law
darcy_law (See: [http://en.wikipedia.org/wiki/Darcy%27s_law Darcy's law]).
darcy_weisbach_equation (See: [http://en.wikipedia.org/wiki/Darcy–Weisbach_equation Darcy-Weisbach]).
diffusion_equation
ehrenfest_equations (See: [http://en.wikipedia.org/wiki/Ehrenfest_equations Ehrenfest equations]).
eikonal_equation (See: [http://en.wikipedia.org/wiki/Eikonal_equation Eikonal equation].)
einstein_field_equations
euler_equation (inviscid flow)
euler_lagrange_equation
exner_equation
faraday_law
faxen_law
fick_law
flint_law
fresnel_equations
friedmann_equations
fourier_law
gauss_law_for_electricity
gauss_law_for_magnetism
gay_lussac_law
geodesic_equation
geometric_optics_equation
gibbs_helmholtz_equation
gibrat_law (See: [http://en.wikipedia.org/wiki/Gibrat%27s_law Gibrat's law].)
glen_stress_strain_law (Glen's Law for glacier flows, Glen (1955); nonnewtonian fluid)
hack_law
### heat_equation (use "diffusion_equation" instead)
helmholtz_equation
henry_law
horton_law
hubble_law
huygens_fresnel_principle (See: [http://en.wikipedia.org/wiki/Huygens–Fresnel_principle Huygens-Fresnel principle].)
ideal_gas_law (See: [http://en.wikipedia.org/wiki/Ideal_Gas_Law Ideal gas law]. Also an "ideal_gas_model" ??)
joule_first_law
joule_second_law
kepler_first_law_of_planetary_motion
kepler_second_law_of_planetary_motion
kepler_third_law_of_planetary_motion
kirchoff_circuit_laws [http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws Kirchoff circuit laws]
kirchoff_diffraction_formula
kirchoff_thermal_radiation_law
laplace_equation
law_of_the_wall (flow resistance)
lorentz_force_law
manning_equation (flow resistance)
mass_energy_equivalence
maxwell_equations
minimal_surface_equation
navier_stokes_equation
nernst_equation (See: [http://en.wikipedia.org/wiki/Nernst_equation Nernst equation].)
newton_first_law_of_motion
newton_law_of_cooling
newton_law_of_universal_gravitation
newton_second_law_of_motion
newton_third_law_of_motion
nonlinear_diffusion_equation ###
ohm_law
p_laplace_equation
planck_law
poiseuille_law
poisson_equation
reynolds_averaged_navier_stokes_equation
richards_equation (infiltration theory)
schroedinger_equation
snell_law
stefan_boltzmann_law
stiff_equation #### (a type, vs. a named equation)
stokes_law
thermodynamics_zeroth_law
thermodynamics_first_law
thermodynamics_second_law
thermodynamics_third_law
wien_displacement_law
young_laplace_equation
zipf_law (See: [http://en.wikipedia.org/wiki/Zipf%27s_Law Zipf's law].)

 


== {{ Bar Heading| text=Inequalities}} ==
:
* These all end in "_inequality".
:
* See [http://en.wikipedia.org/wiki/List_of_inequalities List of Inequalities (Wikipedia)].
:

 


== {{ Bar Heading| text=Identities}} ==
:
* These all end in "_identity".
:
* See [http://en.wikipedia.org/wiki/List_of_mathematical_identities List of Mathematical Identities (Wikipedia)].
:

 


== {{ Bar Heading| text=Approximations}} ==
:
* These all end in "_approximation" and some can be found in other sections.

adiabatic_approximation
binomial_approximation
born_approximation
born-huang_approximation
born-oppenheimer_approximation
boussinesq_approximation (ocean modeling)
central_field_approximation
coherent_potential_approximation
coopmans_approximation (See: [http://en.wikipedia.org/wiki/Coopmans_approximation Coopmans approximation].)
deep_water_wave_approximation
diophantine_approximation (of real numbers by rationals)
eikonal_approximation
empty-lattice_approximation
flat_space-time_approximation
first-order_approximation
fourier_series_approximation
frictionless_approximation
gaussian_approximation
gross-pitaevskii_approximation
heavy_traffic_approximation
infiltrated-depth_approximation (infiltration modeling)
kirkwood_approximation
lanczos_approximation
laurent_series_approximation
linear_approximation
local-density_approximation
low_rank_approximation
mean-field_approximation
minimax_approximation
muffin-tin_approximation
pade_approximation (of functions by rational functions)
patched-conic_approximation
percus-yevick_approximation
perturbation_series_approximation (See: [http://en.wikipedia.org/wiki/Perturbation_theory Perturbation theory].)
power-law_approximation
puiseux_series_approximation
quadratic_approximation
rigid_lid_approximation (## maybe not here?)
second-order_approximation
shallow_water_approximation
shallow_water_wave_approximation
small-angle_approximation (also, paraxial approximation)
spouge_approximation
steady-state_approximation
stirling_approximation
taylor_series_approximation
thin-lense_approximation
two-stream_approximation
wavelet_series_approximation ####
wkb_approximation

 


== {{ Bar Heading| text=Flow-Type Assumptions}} ==
:
* These names all end in "_flow".

accelerating_flow
axisymmetric_flow (in cylindrical coordinates, all theta derivatives are zero)
boundary_layer_flow
converging_flow
couette_flow (See: [http://en.wikipedia.org/wiki/Couette_Flow Couette flow]. Really a "flow model"?)
critical_flow (Froude number = 1. See subcritical & supercritical.)
depth_integrated_flow (for 3D flow to 2D flow; vs. vertically_integrated_flow)
diverging_flow
drag_induced_flow (e.g. Couette flow)
electro_osmotic_flow
fully_developed_flow (i.e. derivatives of velocity with distance in the flow direction vanish)
geostrophic_flow ###### CHECK
hele_shaw_flow (See: [http://en.wikipedia.org/wiki/Hele-Shaw_flow Hele-Shaw flow]. Really a "flow model"?)
high_froude_number_flow
high_reynolds_number_flow
hydraulically_rough_flow
hydraulically_smooth_flow
hydrostatic_flow
hypersonic_flow
inviscid_flow (of an ideal fluid with no viscosity)
isentropic_flow (both adiabatic and reversible; see isentropic_process)
laminar_flow
low_froude_number_flow
low_reynolds_number_flow
nonaccelerating_flow (i.e. the nonlinear inertial term is negligible compared to others)
nonhydrostatic_flow
no_radial_flow (i.e. in cylindrical coordinates, the r component of velocity is zero)
no_swirl_flow (i.e. in cylindrical coordinates, the theta component of velocity is zero; also non-swirling)
plug_flow (See: [http://en.wikipedia.org/wiki/Plug_flow Plug flow]. Sometimes called "piston flow".)
poiseuille_flow (See: [http://en.wikipedia.org/wiki/Poiseuille_flow]. Really a "flow model"?)
potential_flow (irrotational and inviscid, as around airfoils; See [http://en.wikipedia.org/wiki/Potential_flow Potential flow]).
pressure_induced_flow (e.g. Poiseuille flow)
separated_flow
statistically_isotropic_turbulent_flow
steady_flow (all time derivatives equal zero)
stokes_flow (same as "creeping flow"; See: [http://en.wikipedia.org/wiki/Stokes_Flow Stokes flow]).
subcritical_flow (Froude number < 1; see: [http://en.wikipedia.org/wiki/Froude_number Froude number].)
subsonic_flow
supercritical_flow (Froude_number > 1)
supersonic_flow
taylor_couette_flow (Really a flow model?)
taylor_dean_flow (Really a flow model?)
transonic_flow
turbulent_flow
unsteady_flow
variable_area_flow (include this one? see converging and diverging flow; nozzles)
viscous_flow

Note: "reynolds_averaged" is used in "reynolds_averaged_navier_stokes_equation".

 


== {{ Bar Heading| text=Fluid-Type Assumptions}} ==
:
* These names all end in "_fluid". See [http://en.wikipedia.org/wiki/Non-newtonian_fluid Non-newtonian Fluid] and links therein.

* See: [http://en.wikipedia.org/wiki/Fluid_dynamics Fluid dynamics] and links therein.

* The word "material" is often used instead of "fluid" or "solid", especially in the case of material types or models that may occur in either fluid or solid form.

* Most of these assumptions correspond to a particular functional relationship that describes how a fluid or material responds to an applied shear stress. (See: [http://en.wikipedia.org/wiki/Stress–strain_curve stress-strain curve].) These typically involve some combination of (1) shear stress (often denoted by tau or sigma), (2) time derivative of shear stress, and (3) shear strain rate (time derivative of the strain), sometimes abbreviated to "shear rate" or "strain rate" Note that strain is dimensionless and often denoted as epsilon. [http://en.wikipedia.org/wiki/Shear_stress Shear stress] (like pressure) has SI units of Pa. [http://en.wikipedia.org/wiki/Shear_rate Shear rate] (same as [http://en.wikipedia.org/wiki/Strain_rate strain rate]) has SI units of (1/s).

* Glen's Law is a power-law relationship that expresses the shear strain rate as the shear stress to a power, where the power is often n=3. It may be a special case of one of the nonnewtonian fluid types listed here.

bingham_plastic_fluid (See: [http://en.wikipedia.org/wiki/Bingham_plastic Bingham plastic]).
boger_fluid (See: [http://en.wikipedia.org/wiki/Constant_Viscosity_Elastic_(Boger)_Fluids]).
carreau_fluid (See: [http://en.wikipedia.org/wiki/Carreau_fluid]).
casson_fluid (industry standard model for molten milk chocolate)
compressible_fluid
cross_fluid (See: [http://en.wikipedia.org/wiki/Cross_fluid]).
dilatant_fluid (shear thickening fluid or STF)
first_order_fluid
herschel_bulkley_fluid (See: [http://en.wikipedia.org/wiki/Herschel-Bulkley_fluid]).
incompressible_fluid
kelvin_voigt_fluid (a linear viscoelastic model; same as "kelvin_material" ?? ######)
maxwell_fluid (a linear viscoelastic model. See: [http://en.wikipedia.org/wiki/Maxwell_material Maxwell material].)
newtonian_fluid (linear relation between shear stress and strain rate that goes through origin)
nonnewtonian_fluid
oldroyd_fluid (a linear viscoeleastic model; see [http://en.wikipedia.org/wiki/Oldroyd-B_model Oldroyd-B model].
power_law_fluid (generalized Newtonian, Ostward-de Waele)
pseudoplastic_fluid (shear thinning)
quemada_fluid (Used to model blood. See: [http://en.wikipedia.org/wiki/Hemorheology Hemorheology].)
rheopectic_fluid
second_order_fluid
super_fluid (See: [http://en.wikipedia.org/wiki/Superfluid Superfluid]).
thixotropic_fluid (See: [http://en.wikipedia.org/wiki/Thixotropy Thixotropy].)
viscoelastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastic].)
viscoplastic_fluid (See: [http://en.wikipedia.org/wiki/Viscoplastic Viscoplastic].)

Note: Use "inviscid_flow" vs. "inviscid_fluid" and "viscous_flow" vs. "viscous_fluid".

 


== {{ Bar Heading| text=Material-Type Assumptions}} ==
:
* These names all end in "_material".

* There is sometimes a blurred semantic distinction between a "material model" (e.g. Arruda-Boyce model) and just a "material'. There are many named models (see separate section) for mathematical models of materials.

* Some types of materials can exist as either a solid or a fluid, and an extra assumption tag should be used to specify if one or the other is assumed.

* "Material" is used as a generic term. See: [http://en.wikipedia.org/wiki/Materials_science Materials science].)

amorphous_material (e.g. gel, glass; also noncrystalline_material. See: [http://en.wikipedia.org/wiki/Amorphous_solid].)
auxetic_material (See: [http://en.wikipedia.org/wiki/Auxetics Auxetics].)
bio_material (See: [http://en.wikipedia.org/wiki/Biomaterial Biomaterial].)
cauchy_elastic_material (same as simple elastic material)
ceramic_material (See: [http://en.wikipedia.org/wiki/Ceramic_materials Ceramic materials].)
composite_material (See: [http://en.wikipedia.org/wiki/Composite_materials Composite materials].)
compressible_material
crystalline_material (or solid?)
elastic_material (See: [http://en.wikipedia.org/wiki/Elasticity_(physics) Elasticity].)
elastoplastic_material
elastoviscoplastic_material (or solid?)
glass_material (amorphous solid that exhibits a glass transition. See: [http://en.wikipedia.org/wiki/Glass Glass].)
homogeneous_material
hyperelastic_material (See: [http://en.wikipedia.org/wiki/Hyperelastic_material Hyperelastic material]. Also called green elastic material and special case of cauchy elastic material.)
hypoelastic_material (See: [http://en.wikipedia.org/wiki/Hypoelastic_material Hypoelastic material]).
incompressible_material
isotropic_material
kelvin_voigt_material (See: [http://en.wikipedia.org/wiki/Kelvin-Voigt_material Kelvin-Voigt Material].)
linear_elastic_material
maxwell_material (See: [http://en.wikipedia.org/wiki/Maxwell_material].)
mohr_coulomb_material (See: [http://en.wikipedia.org/wiki/Mohr-Coulomb_theory Mohr-Coulomb theory]. Model or material type?)
nonlinear_elastic_material
plastic_material (See: [http://en.wikipedia.org/wiki/Plastic Plastic]. Compare to polymeric material.)
polymeric_material (See: [http://en.wikipedia.org/wiki/Polymer Polymer].)
semicrystalline_material
solid_material (for cases where material may be fluid or solid)
thermoelastic_material
viscoelastic_material (See: [http://en.wikipedia.org/wiki/Viscoelasticity Viscoelastisticity].)
viscoplastic_material (See: [http://en.wikipedia.org/wiki/Viscoplasticity Viscoplasticity].)

 


== {{ Bar Heading| text=Function-Type Assumptions}} ==
:
* These names all end in "_function".
* See Geometry and Shape Assumptions.

analytic_function
bijective_function
chebyshev_polynomial_function
circle_function
complex_valued_function
constant_function
continuous_function
cosine_function
cumulative_distribution_function
daubechies_d2_wavelet_function (actually a whole family, with d2, d4, ..., d20)
decreasing_function
differentiable_function
differentiable_twice_function
dirac_delta_function
discontinuous_function
ellipse_function
exponential_function
gamma_function
gaussian_function
golden_spiral_function
haar_wavelet_function
harmonic_function
hermite_polynomial_function
hermitian_wavelet_function
holomorphic_function (very similar to "analytic_function")
hyperbola_function
identity_function
increasing_function
injective_function
inverse_function
linear_function
log_function
log_spiral_function (See: [http://en.wikipedia.org/wiki/Logarithmic_spiral Log spiral].)
logit_function (See: [http://en.wikipedia.org/wiki/Logit Logit function].)
monotonic_function
negative_function
nondecreasing_function (distinct from "increasing_function")
nonnegative_function
parabola_function (same as "quadratic_function")
periodic_function
polynomial_function
positive_function
power_law_function
probability_density_function
probit_function (See: [http://en.wikipedia.org/wiki/Probit Probit function].)
real_valued_function
ricker_wavelet_function ("mexican hat wavelet")
sawtooth_wave_function
sine_function
sqrt_function
square_wave_function (See: [http://en.wikipedia.org/wiki/Square_wave square wave].)
step_function (See: [http://en.wikipedia.org/wiki/Heaviside_step_function Heaviside step function].)
tanh_function
triangle_wave_function

See: [http://en.wikipedia.org/wiki/List_of_mathematical_functions List of mathematical functions (Wikipedia)].

Note that "multivalued_function" is a misnomer. See: [http://en.wikipedia.org/wiki/Multiple-valued_function multivalued function].)

* These are already included with Probability Distributions
beta_density_function
gompertz_function

* We could have a similar section for '''surfaces'''.
continuous_surface
differentiable_surface
differentiable_twice_surface

 


== {{ Bar Heading| text=Geometric Assumptions}} ==
:
* Most of these names end in "_shaped".
* The polygons here are assumed to be regular polygons. If they aren't, insert the adjective "irregular".
* See: [http://en.wikipedia.org/wiki/Geometry Geometry].

circle_shaped
cone_shaped
cube_shaped
cylinder_shaped
ellipse_shaped
ellipsoid_shaped (e.g. for earth)
half_plane
hexagon_shaped
hyperbola_shaped
octagon_shaped
parabola_shaped
pentagon_shaped
prism_shaped
rectangle_shaped
rhombus_shaped
semicircle_shaped (e.g. for a channel_cross_section)
sphere_shaped
square_pyramid_shaped
square_shaped
trapezoid_shaped (e.g. for a channel_cross_section)
triangular_pyramid_shaped

concave
concave_upward (long profiles)
convex

 


== {{ Bar Heading| text=Exclusions}} ==
:
* These are objects or effects that are neglected or excluded from consideration in a model.
* Only relevant/important exclusions should be reported.
* Most of these names start with "no_".
:
no_aerosols (1 in CF)
no_anthropogenic_effects
no_antrhopogenic_land_use_change (###### 1 in CF; excluding_anthropogenic_land_use_change)
no_baseflow (hydrology) (1 in CF; excluding_baseflow)
no_bioturbation
no_clouds (1 in CF)
no distributaries
no_friction
no_interception (hydrology)
no_litter (on forest floor) (1 in CF; excluding_litter)
no_longwave-radiation
no_macropores
no_overbank_flow
no_radial_flow (explained and duplicated in "Flow type assumptions")
no_rainfall
no_relativistic_effects
no_resistance
no_shadowing
no_shortwave-radiation
no_slipping
no_sloped-terrain
no_swirl_flow (explained and duplicated in "Flow type assumptions")
no_snow (1 in CF)
no_snowfall
no_tides (2 in CF)
no_turbulence
no_vegetation
## no_viscosity (use inviscid_flow)
no_waves

 


== {{ Bar Heading| text=Named Model-Type Assumptions (by Domain)}} ==
:
* These names all end in "_model".

'''Aerodynamics Models'''
clark_x_airfoil_model
clark_y_airfoil_model
clark_z_airfoil_model
eppler_1200_airfoil_model
joukowski_airfoil_model

'''Agent-Based Models'''
agent_based_model (See: [http://en.wikipedia.org/wiki/Agent_based_model Agent-based model].)
reynolds_flocking_model
schelling_segregation_model [http://web.mit.edu/rajsingh/www/lab/alife/schelling.html Schelling segregation model]

'''Atmosphere and Radiation Models'''
boussinesq_approximation (not in CF, but see for_*)
brutsaert_saturated_vapor_pressure_model
clear_sky (23 in CF)
deep_snow (1 in CF)
horizontal_plane_topography (for clear-sky radiation calculation, not in CF)
(OR zero_slope_terrain, OR no_sloped_terrain OR nonsloped_terrain ???
rigid_lid (in CF; always related to boussinesq approximation ??)
satterlund_saturated_vapor_pressure_model
sea_level_for_geoid (4 in CF)
standard_pressure (not in CF)
standard_temperature (not in CF)

'''Chemistry Models'''
atomic_shell_model
bohr_model
nuclear_shell_model (See: [http://en.wikipedia.org/wiki/Nuclear_shell_model nuclear shell model].)
rutherford_model
valence_bond_model
vespr_model (See: [http://en.wikipedia.org/wiki/VSEPR_Theory VESPR theory].)

'''Cosmological Models'''
baum_frampton_model (a cyclic model)
big_bang_model (See: [http://en.wikipedia.org/wiki/Big_bang Big bang]).
big_bounce_model
big_crunch_model
conformal_cyclic_model
cyclic_model
dark_energy_model (and dark_mass_model ?)
lambda_cdm_model (standard model of Big Bang cosmology)
steinhardt_turok_model (a cyclic model)

'''Earthquake Models'''
rough_fault_model
slider_block_model
spring_block_seismic_model
travelling_wave_model (include the word "earthquake"? ####)

'''Ecological Models'''
exponential_growth_model
food_web_model [http://en.wikipedia.org/wiki/Food_web Food web]
kolmogorov_predator_prey_model
logistic_growth_model
lotka_volterra_model [http://en.wikipedia.org/wiki/Predator-prey_interaction Lotka-Volterra]
natural_selection_model [http://en.wikipedia.org/wiki/Natural_selection Natural selection]
population_growth_model
richards_growth_model
trophic_cascade_model [http://en.wikipedia.org/wiki/Trophic_cascade Trophic cascade]

'''Fluid Dynamics Models'''
albertson_2d_turbulent_jet_model
batchelor_vortex_model
burgers_vortex_model
couette_flow_model
free_surface_vortex_model
free_vortex_model (irrotational, velocity proportional to 1/r)
goertler_2d_turbulent_jet_model
hill_spherical_vortex_model
horseshoe_vortex_model
lamb_chaplygin_dipole_vortex_model
lamb_oseen_vortex_model
peckham_2d_turbulent_jet_model
poiseuille_flow_model
rankine_vortex_model
rigid_body_vortex_model (velocity proportional to r)
taylor_couette_flow_model
taylor_dean_flow_model
taylor_green_vortex_model
tollmien_2d_turbulent_jet_model
trailing_vortex_model (or wing_tip_vortex_model)
turbulent_jet_model
vortex_ring_model

'''General Physics Models'''
double_pendulum_model (See: [http://en.wikipedia.org/wiki/Double_pendulum Double pendulum].)
foucault_pendulum_model (See: [http://en.wikipedia.org/wiki/Foucalt_Pendulum Foucault Pendulum].)
harmonic_oscillator_model
quantum_harmonic_oscillator_model
simple_pendulum_model (harmonic oscillator ? gravity pendulum?)
standard_particle_physics_model
vibrating_string_model

'''Geodynamics Models'''
:
:

'''Hydrology: Channelized Flow Models'''
d8_surface_flow_model
diffusive_wave_model ####
d_infinity_surface_flow_model ####
dynamic_wave_model
hydraulic_geometry_at_a_station_model
hydraulic_geometry_downstream_model #### (Leopold et al.)
kinematic_wave_model
law_of_the_wall_flow_resistance_model ##### ???
manning_flow_resistance_model ##### ???
mass_flux_flow_model
muskingum_flow_routing_model (routing flow through a channel network)
rational_regime_model

'''Hydrology: Evaporation (and sometimes Transpiration) Process Models'''
(See: [http://library.wrds.uwyo.edu/wrp/87-06/ch-04.html Methods for estimating ET].)
asce_standardized_evaporation_model (in CUAHSI HIS HydroModeler)
blaney_criddle_evaporation_model
debruin_evaporation_model (lakes and ponds)
energy_balance_evaporation_model
hargreaves_evaporation_model (remove the "s" in hargreaves ??)
jensen_haise_evaporation_model
kohler_nordenson_fox_evaporation_model (lakes and reservoirs)
kohler_parmele_evaporation_model
penman_evaporation_model
penman_monteith_evaporation_model
priestley_taylor_evaporation_model
shuttleworth_evaporation_model (a modified penman model)
stewart_rouse_evaporation_model (lakes and ponds)
thornthwaite_water_balance_model ########

'''Hydrology: Ground Water and Infiltration Modeling Assumptions'''
(also see dupuit_forschheimer in Modeling Methods.)
brooks_corey_soil_model ? ####
confined_aquifer ####
dupuit_assumption
homogeneous_medium (separate from isotropic ??)
horizontal_flowlines (and vertical equipotential lines)
hydraulic_gradient_equals_free_surface_gradient
hydraulic_gradient_equals_land_surface_gradient
hydraulic_gradient_invariant_with_depth
hydrostatic_pressure_head
impermeable_horizontal_base (or impermeable_boundary_at_base)
impermeable_lower_boundary (or impermeable_base)
isotropic_medium
steady_state_recharge ???
transitional_brooks_corey_soil_model ? ####
unconfined_aquifer ####
van_genuchten_soil_model ? ####

'''Hydrology: Infiltration Process Models'''
beven_infiltration_model (assumes Ks decays exponentially)
green_ampt_infiltration_model
horton_infiltration_model
infiltrated_depth_approximation (not in CF) (Used by Green-Ampt and Smith-Parlange)
(or infiltrability_depth_approximation)
philip_infiltration_model
richards_1d_infiltration_model
richards_3d_infiltration_model
scs_curve_number_infiltration_model (remove "curve number"?)
smith_parlange_infiltration_model

'''Hydrology: Snowmelt Models'''
degree_day_snowmelt_model
energy_balance_snowmelt_model

'''Hydrology: Soil Models'''
brooks_corey_soil_model
darcy_soil_model ?###### See Equations, Laws, Etc.
transitional_brooks_corey_soil_model
van_genuchten_soil_model

'''Hydrology: Surface Water Modeling Assumptions'''
bankfull_flow (or maximum inbank flow)
channel_width_less_than_model_cell_width
convergent_topography
convergent_or_divergent_topography ###### ?
d8_flow_between_cells
d_infinity_flow_between_cells
diffusive_wave
dynamic_wave
hydrologically_sound (applied to a DEM)
impermeable_surface ???
inbank_flow (an accepted term; contrast with overbank and bankfull flow)
kinematic_wave (hydraulic_slope_equals_channel_slope)
law_of_the_wall (also listed with equations)
liquid_water_equivalent (used to clarify a quantity like precipitation_rate)
manning_equation (also listed with equations)
mass_flux_method_flow_between_cells
overbank_flow
overland_flow
prismatic_channels
sheet_flow
spatially_uniform_rainfall
#### instantaneous_unit_hydrograph idea ???

'''Illumination and Shading Models'''
See: [http://en.wikipedia.org/wiki/List_of_common_shading_algorithms List of common shading algorithms].
blinn_phong_illumination_model
cook_torrance_illumination_model
flat_shading_model
gouraud_shading_model
lambert_illumination_model (lambert vs. lambertian)
minnaert_illumination_model
oren_nayer_illumination_model
phong_illumination_model
phong_shading_model
ward_anisotropic_illumination_model

'''Infiltration Models (Ventilation Models)'''
lbl_infiltration_model
sherman_grimsrud_infiltration_model

'''Nonlinear Science Models'''
aperiodic_tiling_model (See: [http://en.wikipedia.org/wiki/Aperiodic_tiling Aperiodic tiling].)
bond_percolation_model (what type of lattice ??)
cellular_automata_model
diffusion_limited_aggregation_model
dimer_model (and "double_dimer_model" ?)
ehrenfest_urn_model
fisher_droplet_model
interacting_particle_system_model
ising_model
lattice_gas_model (includes: lattice_gas_automata_model and lattice_boltzmann_model. See: [http://en.wikipedia.org/wiki/Lattice_gas_automaton Lattice gas automaton].)
logistic_map_model
penrose_tiling_model
potts_model (See: [http://en.wikipedia.org/wiki/Potts_model Potts model].)
sandpile_model (Per Bak, self-organized criticality)
self_similar_tree_model
site_percolation_model (what type of lattice ??)
voter_model

'''Ocean Models'''
deep_water_wave
edge_wave
fully_developed_sea
kelvin_wave (coastal or equatorial)
passive_scalar (e.g. temperature and salinity, perhaps suspended sediment)
### per_unit_length_of_wave_crest
rossby_wave
shallow_water_wave
shore_parallel_contours (not in CF)
stokes_wave

'''Sediment Transport Models'''
bagnold_sediment_transport_model (distinguish total load and bedload ####)
detachment_limited_sediment_transport
einstein_sediment_transport_model
komar_longshore_sediment_transport_model ####
meier_peter_mueller_sediment_transport_model
supply_limited_sediment_transport

'''Thermodynamics Models'''
black_body_model (See: [http://en.wikipedia.org/wiki/Black_body Black body].)
carnot_heat_engine_model (See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine]).
gray_body_model
white_body_model

'''Turbulence and Turbulence Closure Models'''
See: [http://en.wikipedia.org/wiki/Turbulence_modeling Turbulence modeling].
detached_eddy_simulation_model (DES)
direct_numerical_simulation_model (DNS) (Navier-Stokes solved without a turbulence model)
eddy_viscosity_model (due to Boussinesq, 1887)
k_epsilon_model (due to Jones and Launder)
k_omega_model (due to Kolmogorov ??)
kolmogorov_statistical_turbulence_model
large_eddy_simulation_model (LES) ?? #####
menter_shear_stress_transport_model
prandtl_mixing_length_model (due to Prandtl)
reynolds_averaged_navier_stokes_model (or reynolds_shear_stress_model)
smagorinsky_model (due to Smagorinsky, 1964; for sub-grid scale eddy viscosity)
spalart_allmaras_model

'''Water Wave Models'''
airy_wave_model [http://en.wikipedia.org/wiki/Airy_wave_theory Airy waves]
capillary_wave_model (type of wave vs. model for waves?)
cnoidal_wave_model [http://en.wikipedia.org/wiki/Cnoidal_wave Cnoidal waves]
kelvin_wave_model [http://en.wikipedia.org/wiki/Kelvin_wave]
korteweg_devries_solitary_wave_model
russell_solitary_wave_model
solitary_wave_model
stokes_wave_model
tsunami_wave_model

:
'''Models Not Yet Grouped'''
general_relativity_model
hagen_poiseuille (pressure drop in a pipe; laminar, viscous, incompressible)
harmonic_function (solution to Laplace equation)
hydraulic_jump
inclined_plane
power_law ####
special_relativity_model
unnamed_empirical_law ####
VSEPR (to compute molecular geometry)
boussinesq_buoyancy_approximation
dispersion_relation (could be linear)
kramers_kronig_relations

 


== {{ Bar Heading| text=Thermodynamic Process Assumptions}} ==
:
* These names all end in "_process". See: [http://en.wikipedia.org/wiki/Thermodynamic_process Wikipedia: Thermodynamic process] and links therein.

adiabatic_process (See: [http://en.wikipedia.org/wiki/Adiabatic_process Adiabatic]).
cyclic_process
diabatic_process
endoreversible_process
endothermic_process (better as adjective? absorbs energy)
exothermic_process (better as adjective? releases energy)
irreversible_process
isentropic_process (also called "reversible" ?; See: [http://en.wikipedia.org/wiki/Isentropic_process Isentropic]).
isenthalpic_process (also called "isoenthalpic"; See: [http://en.wikipedia.org/wiki/Isenthalpic Isenthalpic]).
isobaric_process
isocaloric_process
isochoric_process
isothermal_process
polytropic_process
quasistatic_process (reversible implies quasistatic, but not conversely)
reversible_process
thermal_equilibrium #### (See "black_body_model".) (See: [http://en.wikipedia.org/wiki/Thermal_equilibrium Thermal equilibrium]).

 


== {{ Bar Heading| text=Stochastic Model Assumptions}} ==
:
* Many of these end with the word "_process", which is part of the standard terminology. Many others end with "_distribution".

* See [http://en.wikipedia.org/wiki/Stochastic_process Wikipedia: Stochastic process] and [http://en.wikipedia.org/wiki/List_of_stochastic_processes_topics List of Stochastic Process Topics].

autoregressive
bernoulli_process
bessel_process
birth_death_process
blue_noise_process
branching_process
brownian_bridge_process
brownian_motion_process
buffon_needle_process
cauchy_process
chinese_restaurant_process
colored_noise_process
compound_poisson_process
contact_process
continuous_process
continuous_time_process
counting_process
coverage_process
cox_point_process
diffusion_process
dirichlet_process
discrete_process
discrete_time_process
ergodic_process
feller_process
fractional_brownian_motion_process
galton_watson_process
gaussian_white_noise_process
geometric_brownian_motion_process
grey_noise_process
homogeneous
hunt_process
independent_increments
#### independent_and_identically_distributed (use both)
infinitely_divisible_process
inhomogeneous_poisson_process
ito_diffusion_process
jump_diffusion_process
jump_process
levy_process
linear_least_squares_regression
local_time_process
markov_process
martingale_process
mckean_vlasov_process
moran_process
moving_average
negative (process?)
nonlinear_least_squares_regression
nonnegative (process?)
nonstationary_process
ornstein_uhlenbeck_process
pink_noise_process
point_process
poisson_event_process
poisson_line_process
poisson_point_process
poisson_polygon_process
poisson_process
polya_tree_process
positive (process?)
power_law_noise_process
pure_jump_process
random_multiplicative_cascade_process (is there "additive", too?)
random_tree_process
random_walk_process (symmetric or unsymmetric)
red_noise_process
renewal_process (generalization of Poisson point process)
risk_process
schramm_loewner_evolution_process (See: [http://en.wikipedia.org/wiki/Stochastic_Loewner_evolution SLE process]).
second_order_stationary_process
self_avoiding_random_walk_process
semi_markov_process
shot_noise_process (e.g. raindrops on a roof)
stable_process
stationary_process
storage_process
telegraph_process
uncorrelated
violet_noise_process
weak_stationarity_of_order_k
white_noise_process
wiener_process

 


== {{ Bar Heading| text=Probability Distributions}} ==
:
* Many of these end with the word "_distribution",
* Also see: [http://en.wikipedia.org/wiki/List_of_probability_distributions List of probability distributions] (Wikipedia).
* Most of these are '''named''' distributions, but some are a '''type''' of distribution (e.g. discrete distribution).
:
arcsine_distribution (See: [http://en.wikipedia.org/wiki/Arcsine_distribution Arcsine distribution].)
bates_distribution (See: [http://en.wikipedia.org/wiki/Bates_distribution Bates distribution].)
benford_distribution (See: [http://en.wikipedia.org/wiki/Benford%27s_law Benford's law].)
bernoulli_distribution (See: [http://en.wikipedia.org/wiki/Bernoulli_distribution Bernoulli distribution].)
beta_distribution (See: [http://en.wikipedia.org/wiki/Beta_distribution Beta distribution].)
beta-binomial_distribution (See: [http://en.wikipedia.org/wiki/Beta-binomial_distribution Beta-binomial distribution].)
beta-prime_distribution (See: [https://en.wikipedia.org/wiki/Beta_prime_distribution Beta prime distribution].)
bimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
binomial_distribution (See: [http://en.wikipedia.org/wiki/Binomial_distribution Binomial distribution].)
boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Boltzmann_distribution Boltzmann distribution].)
borel_distribution (See: [http://en.wikipedia.org/wiki/Borel_distribution Borel distribution].)
borel-tanner_distribution
burr_distribution (See: [https://en.wikipedia.org/wiki/Burr_distribution Burr distribution].)
cauchy_distribution (See: [http://en.wikipedia.org/wiki/Cauchy_distribution Cauchy distribution].)
champernowne_distribution (See: [http://en.wikipedia.org/wiki/Champernowne_distribution Champernowne distribution].)
chi-squared_distribution
continuous_distribution
continuous_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(continuous) Uniform distribution (continuous)].)
dagum_distribution (See: [https://en.wikipedia.org/wiki/Dagum_distribution Dagum distribution].)
dirichlet_distribution (See: [https://en.wikipedia.org/wiki/Dirichlet_distribution Dirichlet distribution].)
dirichlet-multinomial_distribution (See: [http://en.wikipedia.org/wiki/Dirichlet-multinomial_distribution Dirichlet-multinomial distribution].)
discrete_distribution
discrete_uniform_distribution (See: [http://en.wikipedia.org/wiki/Uniform_distribution_(discrete) Uniform distribution (discrete)].)
elliptical_distribution (See: [http://en.wikipedia.org/wiki/Elliptical_distribution Elliptical distribution].)
exponential_distribution (See: [http://en.wikipedia.org/wiki/Exponential_distribution Exponential distribution].)
first-contact_distribution (See: [http://en.wikipedia.org/wiki/Spherical_contact_distribution_function Spherical contact distribution].)
frechet_distribution (See: [http://en.wikipedia.org/wiki/Fréchet_distribution Frechet distribution].)
gamma_distribution (See: [http://en.wikipedia.org/wiki/Gamma_distribution Gamma distribution].)
gaussian_distribution (See: [https://en.wikipedia.org/wiki/Normal_distribution Normal distribution].)
generalized_extreme_value_distribution (See: [http://en.wikipedia.org/wiki/Generalized_extreme_value_distribution GEV distribution].)
generalized_pareto_distribution
geometric_distribution (See: [http://en.wikipedia.org/wiki/Geometric_distribution Geometric distribution].)
geometric-stable_distribution (See: [http://en.wikipedia.org/wiki/Geometric_stable_distribution Geometric stable distribution].)
gompertz_distribution (See: [http://en.wikipedia.org/wiki/Gompertz_function Gompertz function].)
gumbel_distribution (See: [http://en.wikipedia.org/wiki/Gumbel_distribution Gumbel distribution].)
half-normal_distribution (See: [http://en.wikipedia.org/wiki/Half-normal_distribution Half-normal distribution].)
hitting-time_distribution (See: [http://en.wikipedia.org/wiki/Hitting_time Hitting time].)
holtsmark_distribution (See: [http://en.wikipedia.org/wiki/Holtsmark_distribution Holtsmark distribution].)
hyperbolic_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_distribution Hyperbolic distribution].)
hyperbolic-secant_distribution (See: [http://en.wikipedia.org/wiki/Hyperbolic_secant_distribution Hyperbolic secant distribution].)
hypergeometric_distribution (See: [http://en.wikipedia.org/wiki/Hypergeometric_distribution Hypergeometric distribution].)
identically_distributed ####
independently_distributed #####
inverse-gamma_distribution (See: [http://en.wikipedia.org/wiki/Inverse-gamma_distribution Inverse-gamma distribution].)
inverse-gaussian_distribution (See: [http://en.wikipedia.org/wiki/Inverse_Gaussian_distribution Inverse Gaussian distribution].)
irwin-hall_distribution (See: [http://en.wikipedia.org/wiki/Irwin–Hall_distribution Irwin-Hall distribution].)
joint-probability_distribution (See: [http://en.wikipedia.org/wiki/Joint_probability_distribution Joint probability distribution].)
kent_distribution (See: [http://en.wikipedia.org/wiki/Kent_distribution Kent distribution].)
landau_distribution (See: [http://en.wikipedia.org/wiki/Landau_distribution Landau distribution].)
laplace_distribution (See: [http://en.wikipedia.org/wiki/Laplace_distribution Laplace distribution].)
levy_distribution (See: [http://en.wikipedia.org/wiki/Lévy_distribution Levy distribution].)
log-cauchy_distribution (See: [http://en.wikipedia.org/wiki/Log-Cauchy_distribution Log-Cauchy distribution].)
log-logistic_distribution (See: [http://en.wikipedia.org/wiki/Log-logistic_distribution Log-logistic distribution].)
log-normal_distribution (See: [http://en.wikipedia.org/wiki/Log-normal_distribution Log-normal distribution].)
log-poisson_distribution
log-symmetric_distribution
logarithmic_distribution (See: [http://en.wikipedia.org/wiki/Logarithmic_distribution Logarithmic distribution].)
logistic_distribution (See: [http://en.wikipedia.org/wiki/Logistic_distribution Logistic distribution].)
logit-normal_distribution (See: [http://en.wikipedia.org/wiki/Logit-normal_distribution Logit-normal distribution].)
maximum_entropy_probability_distribution (See: [http://en.wikipedia.org/wiki/Maximum_entropy_probability_distribution Max entropy pdf].)
maxwell-boltzmann_distribution (See: [http://en.wikipedia.org/wiki/Maxwell–Boltzmann_distribution Maxwell-Boltzmann distribution].)
mixture_distribution (See: [http://en.wikipedia.org/wiki/Mixture_distribution Mixture distribution].)
multimodal_distribution (See: [http://en.wikipedia.org/wiki/Multimodal_distribution Multimodal distribution].)
multinomial_distribution (See: [http://en.wikipedia.org/wiki/Multinomial_distribution Multinomial distribution].)
nakagami_distribution (See: [http://en.wikipedia.org/wiki/Nakagami_distribution Nakagami distribution].)
negative-binomial_distribution (See: [http://en.wikipedia.org/wiki/Negative_binomial_distribution Negative binomial distribution].)
parabolic-fractal_distribution (See: [http://en.wikipedia.org/wiki/Parabolic_fractal_distribution Parabolic fractal distribution].)
pareto_distribution (See: [http://en.wikipedia.org/wiki/Pareto_distribution Pareto distribution].)
pascal_distribution (special case of negative binomial.)
pearson_distribution (See: [http://en.wikipedia.org/wiki/Pearson_distribution Pearson distribution].)
poisson_distribution (See: [http://en.wikipedia.org/wiki/Poisson_distribution Poisson distribution].)
poisson-binomial_distribution (See: [http://en.wikipedia.org/wiki/Poisson_binomial_distribution Poisson binomial distribution].)
polya_distribution (special case of negative binomial)
rademacher_distribution (See: [http://en.wikipedia.org/wiki/Rademacher_distribution Rademacher distribution].)
rayleigh_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_distribution Rayleigh distribution].)
rayleigh-mixture_distribution (See: [http://en.wikipedia.org/wiki/Rayleigh_mixture_distribution Rayleigh mixture distribution].)
reciprocal_distribution (See: [http://en.wikipedia.org/wiki/Reciprocal_distribution Reciprocal distribution].)
rice_distribution (See: [http://en.wikipedia.org/wiki/Rice_distribution Rice distribution].)
skellam_distribution (See: [http://en.wikipedia.org/wiki/Skellam_distribution Skellam distribution].)
skew-normal_distribution (See: [http://en.wikipedia.org/wiki/Skew_normal_distribution Skew normal distribution].)
slash_distribution (See: [http://en.wikipedia.org/wiki/Slash_distribution Slash distribution].)
stable_distribution (See: [http://en.wikipedia.org/wiki/Stable_distribution Stable distribution].)
student-t_distribution (See: [http://en.wikipedia.org/wiki/Student%27s_t-distribution Student's t-distribution].)
symmetric_distribution (See: [http://en.wikipedia.org/wiki/Symmetric_probability_distribution Symmetric distribution].)
tracy-widom_distribution (See: [http://en.wikipedia.org/wiki/Tracy–Widom_distribution Tracy-Widom distribution].)
triangular_distribution (See: [http://en.wikipedia.org/wiki/Triangular_distribution Triangular distribution].)
truncated_distribution (See: [http://en.wikipedia.org/wiki/Truncated_distribution Truncated distribution].)
tukey-lambda_distribution (See: [http://en.wikipedia.org/wiki/Tukey_lambda_distribution Tukey lambda distribution].)
u-quadratic_distribution (See: [http://en.wikipedia.org/wiki/U-quadratic_distribution U-quadratic distribution].)
unimodal_distribution
voigt_distribution (See: [http://en.wikipedia.org/wiki/Voigt_profile Voigt profile].)
von-mises_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises_distribution von Mises distribution].)
von-mises-fisher_distribution (See: [http://en.wikipedia.org/wiki/Von_Mises–Fisher_distribution von Mises-Fisher distribution].)
weibull_distribution (See: [http://en.wikipedia.org/wiki/Weibull_distribution Weibull distribution].)
yule-simon_distribution (See: [http://en.wikipedia.org/wiki/Yule–Simon_distribution Yule-Simon distribution].)
zeta_distribution (See: [http://en.wikipedia.org/wiki/Zeta_distribution Zeta distribution].)
zipf_distribution (See: [http://en.wikipedia.org/wiki/Zipf%27s_law Zipf's law].)

 


== {{ Bar Heading| text=Statistical Operation Assumptions}} ==
:
* Perhaps this should be generalized to something like "Data Transformation Assumptions"?
* These names currently all end with "averaged".
* For ones that start with a unit of time, one of those units is assumed. A number can be inserted in front, when necessary, as in "two_day_averaged".

cell_averaged
day_averaged
depth_averaged
domain_averaged
hour_averaged
interval_averaged
month_averaged
population_averaged
sample_averaged
section_averaged
time_averaged
vertically_averaged
watershed_averaged
year_averaged

 


== {{ Bar Heading| text=Mathematical Assumptions}} ==
:
algebraic (equation)
bijection
bounded (set)
closed (set, curve)
compact (set)
complex-valued
conformal
constant_coefficients (equation or polynomial)
continuous
continuum (continuum_hypothesis ?)
contraction_mapping
countably_infinite
degenerate
differentiable
differentiable_twice
differentiable_three_times
differential (equation)
discontinuous
equal_mixed_partials
finite
fixed_point
ill-posed
infinite
injective
integer-valued
invertible
irrational
jordan_curve
linear
multiple_valued_function ### (misnomer)
negative
nonlinear
nonnegative
orthogonal
permutation
positive
projection
rational
real-valued
spatially_uniform
superposition
symmetric
time_space_substitution
uncountably_infinite
uniform
weak_solution
well-posed

 


== {{ Bar Heading| text=Numerical Grid Assumptions}} ==
:
* Most of these end with the word '''grid'''.
* The word "grid" is used to include the word "mesh".
:
adaptive_grid
arakawa_a_grid (unstaggered)
arakawa_b_grid (staggered)
arakawa_c_grid (staggered)
arakawa_d_grid (staggered, rotated 90 degrees)
arakawa_e_grid (staggered, rotated 45 degrees)
arakawa_u_component (attached to an input var)
arakawa_v_component (attached to an input var)
arakawa_w_component (attached to an input var)
block_structured_grid
boundary-fitted_grid (also called "body-fitted")
delaunay_triangle_grid
hexagon_grid
orthogonal_curvilinear_grid
rectilinear_grid
square_grid
staggered_grid (###### already in arakawa system ??)
structured_grid
triangle_grid
uniform_grid
unstructured_grid
voronoi_polygon_grid

 


== {{ Bar Heading| text=Numerical Method Assumptions}} ==
:
* These are used to describe the numerical method that a model uses to solve the equations it uses to compute variables of interest. The equations could be ODEs, PDEs, algebraic equations (e.g. root finding), etc. We probably don't need separate assumption names like "ode" and "pde" because that is implied by the equation name. See Equations, Laws and Principles for a standardized list of equation names.
* Most of these names end with "_method", "_scheme" or "_grid".
* See: [http://en.wikipedia.org/wiki/List_of_Runge–Kutta_methods List of Runge-Kutta methods].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_ordinary_differential_equations Numerical methods for ODEs].
* See: [http://en.wikipedia.org/wiki/List_of_numerical_analysis_topics#Numerical_methods_for_partial_differential_equations Numerical methods for PDEs].
:
a-stable_method
absolutely-stable_method
adams-bashforth_method
adaptive_mesh_refinement_method (See: [http://en.wikipedia.org/wiki/Adaptive_mesh_refinement Adaptive mesh refinement].)
adaptive_stepsize_method (See: [http://en.wikipedia.org/wiki/Adaptive_stepsize Adaptive stepsize].)
adjoint_state_method (See: [http://en.wikipedia.org/wiki/Adjoint_state_method Adjoint state method].)
analytic_element_method (See: [http://en.wikipedia.org/wiki/Analytic_element_method: Analytic element method]).
backward_difference_scheme
backward_euler_method (See: [http://en.wikipedia.org/wiki/Backward_Euler_method Backward Euler method].)
boundary_element_method (See: [http://en.wikipedia.org/wiki/Boundary_element_method Boundary element method].)
central_difference_scheme (See: [http://en.wikipedia.org/wiki/Central_differencing_scheme Central differencing scheme].)
characteristics_method (known as "method of characteristics")
collocation_method (See: [http://en.wikipedia.org/wiki/Collocation_method Collocation method].)
conditionally_stable_method
conjugate_gradient_method (See: [http://en.wikipedia.org/wiki/Conjugate_gradient_method Conjugate gradient method].)
consistent_method
convergent_method
crank-nicolson_method (See: [http://en.wikipedia.org/wiki/Crank–Nicolson_method Crank-Nicolson method].)
direct_numerical_solution
discrete_element_method (See: [http://en.wikipedia.org/wiki/Discrete_element_method Discrete element method].)
discrete_event_simulation (See: [http://en.wikipedia.org/wiki/Discrete_event_simulation Discrete event simulation].)
dynamic_relaxation_method (See: [http://en.wikipedia.org/wiki/Dynamic_relaxation Dynamic relaxation].)
euler_method (See: [http://en.wikipedia.org/wiki/Euler_method Euler method].) (distinguish between "forward" and "backward" with a prefix?)
explicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
fast_marching_method (See: [http://en.wikipedia.org/wiki/Fast_marching_method Fast marching method], a type of level_set_method.)
finite_difference_method (See: [http://en.wikipedia.org/wiki/Finite_difference_method Finite difference method].)
finite_element_method (See: [http://en.wikipedia.org/wiki/Finite_element_method Finite element method].)
finite_volume_method (See: [http://en.wikipedia.org/wiki/Finite_volume_method Finite volume method].)
first_order_accurate
five-point_stencil_method (See: [http://en.wikipedia.org/wiki/Five-point_stencil Five-point stencil].)
forward_difference_scheme
forward_time_centered_space_scheme (FTCS scheme)
galerkin_method (See: [http://en.wikipedia.org/wiki/Galerkin_method Galerkin method].)
gauss-legendre_method (See: [http://en.wikipedia.org/wiki/Gauss–Legendre_method Gauss-Legendre method].)
gauss-seidel_method (See: [http://en.wikipedia.org/wiki/Gauss–Seidel_method Gauss-Seidel method].)
halley_method (See: [http://en.wikipedia.org/wiki/Halley%27s_method Halley's method].)
heun_method (See: [http://en.wikipedia.org/wiki/Heun%27s_method Heun's method].)
implicit_method (See: [http://en.wikipedia.org/wiki/Explicit_and_implicit_methods Explicit and implicit methods].)
interior_point_method (See: [http://en.wikipedia.org/wiki/Interior_point_method Interior point method].)
iterative_method (See: [http://en.wikipedia.org/wiki/Iterative_method Iterative method].)
l-stable_method (See: [http://en.wikipedia.org/wiki/L-stability L-stability].)
landweber_iteration_method (See: [http://en.wikipedia.org/wiki/Landweber_iteration Landweber iteration].)
large_eddy_simulation
lattice_boltzmann_method (See: [http://en.wikipedia.org/wiki/Lattice_Boltzmann_methods Lattice Boltzmann methods].)
lax-friedrichs_method (See: [http://en.wikipedia.org/wiki/Lax–Friedrichs_method Lax-Friedrichs method].)
lax-wendroff_method (See: [http://en.wikipedia.org/wiki/Lax–Wendroff_method Lax-Wendroff method].)
leapfrog_method
level_set_method (See: [http://en.wikipedia.org/wiki/Level_set_method Level set method].)
linear_multistep_method (See: [http://en.wikipedia.org/wiki/Linear_multistep_method Linear multistep method].)
maccormack_method (See: [http://en.wikipedia.org/wiki/MacCormack_method MacCormack method].)
meshfree_method (See: [http://en.wikipedia.org/wiki/Meshfree_methods Meshfree method].)
midpoint_method (See: [http://en.wikipedia.org/wiki/Midpoint_method Midpoint method].)
multigrid_method (See: [http://en.wikipedia.org/wiki/Multigrid_method Multigrid method].)
newton_raphson_method (See: [http://en.wikipedia.org/wiki/Newton%27s_method Newton's method]; also see "halley_method".)
numerov_method (See: [http://en.wikipedia.org/wiki/Numerov%27s_method Numerov's method].)
particle-in-cell_method (See: [http://en.wikipedia.org/wiki/Particle-in-cell Particle in cell].)
predictor-corrector_method (See: [http://en.wikipedia.org/wiki/Predictor–corrector_method Predictor-corrector method].)
rayleigh-ritz_method (See: [http://en.wikipedia.org/wiki/Rayleigh–Ritz_method Rayleigh-Ritz method].)
relatively_stable_method
relaxation_method (See: [http://en.wikipedia.org/wiki/Relaxation_(iterative_method) Relaxation (iterative method)].)
runge_kutta_method (See: [http://en.wikipedia.org/wiki/Runge–Kutta_methods Runge-Kutta methods]. There are several distinct types.)
second-order_accurate_method
shooting_method (See: [http://en.wikipedia.org/wiki/Shooting_method Shooting method].)
spectral_method (See: [http://en.wikipedia.org/wiki/Spectral_method Spectral method].)
split-step_method (See: [http://en.wikipedia.org/wiki/Split-step_method Split-step method].)
strongly_stable_method
successive_over_relaxation_method (See: [http://en.wikipedia.org/wiki/Successive_over-relaxation Successive over-relaxation].)
trapezoidal_rule_method (See: [http://en.wikipedia.org/wiki/Trapezoidal_rule_(differential_equations) Trapezoidal rule].)
unconditionally_stable_method
unstable_method
upwind_difference_scheme (See: [http://en.wikipedia.org/wiki/Upwind_differencing_scheme_for_convection Upwind difference scheme].)
upwind_first-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_second-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
upwind_third-order_scheme (See: [http://en.wikipedia.org/wiki/Upwind_scheme Upwind scheme].)
verlet_integration_method (See: [http://en.wikipedia.org/wiki/Verlet_integration Verlet integration].)



== {{ Bar Heading| text=State of Matter Assumptions}} ==
:
* These can be provided when the model involves a substance (object) like water that could be in any of several possible states. See: [http://en.wikipedia.org/wiki/States_of_matter States of matter].
* Note that "liquid_equivalent" can also be inserted in quantity names such as "liquid_equivalent_precipitation_rate" to create a single quantity that can accommodate multiple states of matter.
:
gas_phase
liquid_phase
plasma_phase
solid_phase



== {{ Bar Heading| text=System State Assumptions}} ==
:
asymptotic_equilibrium
bistable
dynamic_equilibrium
equilibrium
ergodic
metastable (See: [http://en.wikipedia.org/wiki/Metastability Metastability]).
stable
static_equilibrium
steady_state
unstable
unsteady_state

 


== {{ Bar Heading| text=CF Convention Standard Name Assumptions}} ==
:
* [http://cf-pcmdi.llnl.gov/documents/cf-standard-names/ '''CF Convention Standard Names'''] often include additional information and assumptions in the name itself. The ones in this section were found in the list of CF Standard Names and the number of occurrences found is listed in parentheses. It is not yet clear how some of these should be captured with standard assumption names.

* Many of these are '''Location Assumptions'''.

above_geoid (3 in CF)
above_land_surface (not in CF)
above_reference_datum (1 in CF)
above_reference_ellipsoid (5 in CF)
above_sea_floor (1 in CF)
above_sea_floor_surface (not in CF)
above_sea_level (1 in CF)
above_threshold (5 in CF)

at_*** (51 in CF)
at_cloud_base (1 in CFFl
at_cloud_top (3 in CF)
at_equilibrium (not in CF)
at_freezing_level (1 in CF)
at_land_surface (not in CF; e.g. air pressure)
at_maximum_upward_derivative (1 in CF)
at_saturation (4 in CF)
at_sea_floor (3 in CF)
at_sea_floor_surface (not in CF; e.g. water pressure)
at_sea_ice_base (8 in CF)
at_sea_level (1 in CF)
at_top_of_*** (3 in CF)
at_bottom_*** (not in CF)

assuming_*** (33 in CF)
assuming_clear_sky (24 in CF)
assuming_deep_snow (1 in CF, for surface_albedo)
assuming_no_aerosol_or_cloud (1 in CF)
assuming_no_snow (1 in CF, for surface_albedo)
assuming_no_tide (2 in CF)
assuming_sea_level_for_geoid (4 in CF)

below_geoid (1 in CF)
below_sea_level (1 in CF)
below_sea_surface (1 in CF)
below_surface (1 in CF)
below_threshold (3 in CF)

between_air_and_sea_water (1 in CF)
between_sea_water_and_air (2 in CF)

due_to_*** (399 in CF)
due_to_all_land_processes (2 in CF)
due_to_convective_cloud (1 in CF)
due_to_diffusion (18 in CF)
due_to_dry_convection (1 in CF)
due_to_dry_deposition (35 in CF)
due_to_dry_troposphere (1 in CF)
due_to_dust_ambient_aerosol (2 in CF)
due_to_emission_from_grazing (in CF)

excluding_anthropogenic_land_use_change (in CF)
excluding_baseflow (in CF)
excluding_litter (in CF)

expressed_as_*** (140 in CF)
expressed_as_carbon (67 in CF)
expressed_as_chlorine (7 in CF)
expressed_as_nitrogen (24 in CF)

for_*** (13 in CF)
for_biomass_growth (1 in CF)
for_biomass_maintenance (1 in CF)
for_boussinesq_approximation (1 in CF)
for_momentum (2 in CF; both "for_momentum_in_air")

per_capita
per_unit_area (already used in CF)
per_unit_length_of_wave_crest
per_unit_mass (already used in CF, and synonym for "specific")
per_unit_time ??
per_unit_width (e.g. discharge_per_unit_width)
(see CF: sea_water_transport_across_line,
and "transport_across_unit_distance")

:
:
:

CSN Quantity Templates

2015-07-14T20:53:39Z

Peckhams: /* {{ Bar Heading| text=Miles per Gallon}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). This is now done in the object part of the name, by using either "water~incoming" or "water~outgoing".
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "consumption_rate" ["gallons per mile" or "liters per km"] (of fuel) 
  "fuel-economy" ["miles per gallon" or "km per liter"] 
  "mass-specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile__fuel-economy
automobile_fuel__mass-specific_energy_content

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 


== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel consumption rate" and "fuel economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.
:
* See: [https://en.wikipedia.org/wiki/Fuel_economy_in_automobiles Fuel economy (automobiles)].

 


== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" is a volume per unit area and unit time, and therefore has units of [length / time] (e.g. mm per hour). A "precipitation_mass_flux" is a mass per unit area and unit time, and therefore has units of [mass / (area * time)] (e.g. kg per square meter per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquids. In the CSDMS Standard Names, the object that is precipitating is specified in the object part of the name, such as "water", or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liqui-equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid-equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
:

CSN Quantity Templates

2015-07-14T20:52:01Z

Peckhams: /* {{ Bar Heading| text=Fuel Efficiency}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). This is now done in the object part of the name, by using either "water~incoming" or "water~outgoing".
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "consumption_rate" ["gallons per mile" or "liters per km"] (of fuel) 
  "fuel-economy" ["miles per gallon" or "km per liter"] 
  "mass-specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile__fuel-economy
automobile_fuel__mass-specific_energy_content

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 


== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel_consumption" and "fuel_economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.

 

== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" is a volume per unit area and unit time, and therefore has units of [length / time] (e.g. mm per hour). A "precipitation_mass_flux" is a mass per unit area and unit time, and therefore has units of [mass / (area * time)] (e.g. kg per square meter per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquids. In the CSDMS Standard Names, the object that is precipitating is specified in the object part of the name, such as "water", or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liqui-equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid-equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
:

CSN Quantity Templates

2015-07-14T20:48:26Z

Peckhams: /* {{ Bar Heading| text=Precipitation}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). This is now done in the object part of the name, by using either "water~incoming" or "water~outgoing".
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "consumption_rate" ["gallons per mile" or "liters per km"] (of fuel) 
  "fuel-economy" ["miles per gallon" or "km per liter"] 
  "mass-specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile__fuel-economy
automobile_fuel__mass-specific_energy_content

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* Is there a good "process - rate" quantity name for "fuel_economy" ? We could potentially replace "economy" with "per_gallon_miles".
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 


== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel_consumption" and "fuel_economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.

 

== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" is a volume per unit area and unit time, and therefore has units of [length / time] (e.g. mm per hour). A "precipitation_mass_flux" is a mass per unit area and unit time, and therefore has units of [mass / (area * time)] (e.g. kg per square meter per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquids. In the CSDMS Standard Names, the object that is precipitating is specified in the object part of the name, such as "water", or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liqui-equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid-equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
:

CSN Quantity Templates

2015-07-14T20:42:40Z

Peckhams: /* {{ Bar Heading| text=Fuel Efficiency}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). This is now done in the object part of the name, by using either "water~incoming" or "water~outgoing".
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "consumption_rate" ["gallons per mile" or "liters per km"] (of fuel) 
  "fuel-economy" ["miles per gallon" or "km per liter"] 
  "mass-specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile__fuel-economy
automobile_fuel__mass-specific_energy_content

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* Is there a good "process - rate" quantity name for "fuel_economy" ? We could potentially replace "economy" with "per_gallon_miles".
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 


== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel_consumption" and "fuel_economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.

 

== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" has units of [length / time] (e.g. mm per hour) and a "precipitation_mass_flux" has units of [mass / time] (e.g. kg per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquid water. The CSDMS Standard Names avoid this issue by using the process name "precipitation" instead of "rainfall" or "raining" and then specifying the object that is precipitating, such as "water" or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liquid_equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid_equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
:

CSN Quantity Templates

2015-07-14T06:50:45Z

Peckhams: /* {{ Bar Heading| text=Discharge or Volume Flow Rate}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). This is now done in the object part of the name, by using either "water~incoming" or "water~outgoing".
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "fuel_consumption_rate" ["gallons per mile" or "liters per km"] 
  "fuel_economy" ["miles per gallon" or "km per liter"] 
  "fuel_specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile_fuel__economy
automobile_fuel__specific_energy_content (or energy-per-mass_content ??) #####

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* Is there a good "process - rate" quantity name for "fuel_economy" ? We could potentially replace "economy" with "per_gallon_miles".
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 

== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel_consumption" and "fuel_economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.

 

== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" has units of [length / time] (e.g. mm per hour) and a "precipitation_mass_flux" has units of [mass / time] (e.g. kg per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquid water. The CSDMS Standard Names avoid this issue by using the process name "precipitation" instead of "rainfall" or "raining" and then specifying the object that is precipitating, such as "water" or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liquid_equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid_equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
:

CSN Quantity Templates

2015-07-14T06:48:56Z

Peckhams: /* {{ Bar Heading| text=Discharge or Volume Flow Rate}} */

=   '''[[CSDMS_Standard_Names | CSDMS Standard Names]] — Quantity Templates ''' =
:
* A CSDMS Standard Name must have an '''''object part''''' and a '''''quantity part''''', with adjectives and modifiers (as prefixes) being used to help avoid ambiguity and identify a specific object and a specific, associated quantity. This document contains "quantity templates". For "object templates", see: [[CSN_Object_Templates | '''CSDMS Object Templates''']].
:
* The "templates" listed below are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates will continue to be added over time.
:
* This page used to contain sections with titles like "Attributes of Channels". All of these sections have been moved to a separate page: [[CSN_Examples | '''CSDMS Standard Name Examples''']].
:
* Each template includes examples and explanatory notes, and many of them make reference to the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], sometimes using the abbreviation "CF".
:
* '''''Quantity''''' seems to be the best word choice here, see [http://en.wikipedia.org/wiki/Quantity Quantity] and [http://en.wikipedia.org/wiki/Physical_quantities Physical quantities]. The word "attribute" is more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. Here we define a '''''quantity''''' as an attribute of an object that has units. (But including dimensionless units like [m/m].)
:
* '''''Quantity Suffix Pattern.''''' A "quantity suffix" is a word like "anomaly", "component", "correction", "fraction", "increment", "limit", "magnitude", "offset", "scale", "step" or "threshold" (and in some cases "ratio") that produces a new quantity name from an existing quantity name (e.g. "elevation_increment", "time_step" and "length_scale"). The units are usually unchanged, but "fraction" and "ratio" are exceptions. While quantity suffixes are a common pattern in describing quantities, CSDMS is moving away from using them in standard names because they can also be expressed (with more flexibility) using an '''''operation prefix'''''. ( See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].) For example, "east_velocity_component" can be expressed as "east_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "east_down_component_of_shear_stress". In addition, operations can be composed, as in "x_component_of_gradient_of_elevation", again without losing parsability.
:
* '''''Operation_name + Quantity Pattern'''''. An optional operation name can be added in front of a quantity name to create a new quantity name that often has different units. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].
:
* '''''Process_name + Quantity Pattern'''''. Many quantity names contain a '''''process name''''' modifier from the standardized list of [[CSN_Process_Names | '''CSDMS Process Names''']]. Process names are nouns, not adjectives, so we would use "refraction_index" instead of "refractive_index". (Or "diffusion_coefficient" vs. "diffusive_coefficient", etc.) The templates for Process Attributes and Rates of Processes below provide many more examples.
:
* '''''Object-in-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is contained within the other. Examples include: "concentration", "diffusion_coefficient", "partial_pressure", "relative_saturation" (see Humidity), "solubility" and "volume_fraction". CSDMS has experimented with using the reserved word "_in_" and the pattern: object = (object + "_in_" + object) for such cases as in:

carbon_dioxide_in_air + partial_pressure
carbon_dioxide_in_air + relative_saturation
carbon_dioxide_in_water + solubility
clay_in_soil + volume_fraction
helium_plume_in_air + richardson_number
sand_in_soil + volume_fraction
silt_in_soil + volume_fraction
visible_light_in_air + speed ## (possibly; See the Constants in Physics template.)
water_vapor_in_air + dew_point_temperature
water_in_atmosphere + precipitation_leq-volume_flux

:However, using this pattern causes related quantities to become alphabetically separated, like "clay_in_soil" + "volume_fraction" and "sand_in_soil" + "volume_fraction". For this reason, CSDMS is moving toward expressing the "in" relationship through object nesting (as used in the Part of Another Object Pattern). The examples listed above then become:

air_helium-plume__richardson_number
air_radiation~visible__speed
atmosphere_air_carbon-dioxide__partial_pressure
atmosphere_air_carbon-dioxide__relative_saturation
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_water__precipitation_leq-volume_flux
soil_clay__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
water_carbon-dioxide__solubility
:
:As of 7/23/14, hyphens are used in certain contexts to bundle multiple words that are part of a single concept or object, such as "carbon-dioxide". This allows the object part of a name to be parsed (on underscores) into its component parts. For example, "atmosphere_carbon-dioxide" can be parsed into "atmosphere" and "carbon-dioxide". Without the hyphen, "carbon" and "dioxide" would be identified as two separate objects, with "dioxide' contained in (or a part of) "carbon".
:
:Note that bubble_point_temperature, dew_point_temperature and frost_point_temperature also require one substance within another, as in: air_water~vapor__dew_point_temperature. See the Temperature template.
:
* '''''Saturated Quantity Rule'''''. When using the '''Object-in-object Quantity Pattern''' there are several quantities that refer to a system that is saturated or "at saturation". In these cases the word "saturated" is inserted in front of the quantity name to define a new quantity. Examples include:
air_water~vapor__saturated_partial_pressure
soil_water__saturated_hydraulic_conductivity
soil_water__saturated_volume_fraction (i.e. water content)
: While it is true that the soil is saturated in the first two examples, we use this rule instead of inserting "saturated" as an adjective in front of soil and instead of appending a suffix like "at_saturation", which doesn't fit our (object + quantity) pattern. This rule is natural in the sense that each of the "saturated quantities" listed above would be represented by a separate variable in a model, often denoted with a subscript such as "s".
:
* '''''Object-on-Object Quantity Pattern'''''. Some quantities require 2 objects/substances to be specified where one is "on" or in contact with the other. Examples often involve friction. In such cases we use the reserved word "_on_" and the pattern: object = (object + "_on_" + object), as in:

concrete_rubber__kinetic_friction_coefficient
pavement_rubber__static_friction_coefficient

'''Note:''' Maybe "-and-"or "-to-" would be better than "_on_" here. We should also list
the two object names in alphabetical order to avoid two names for the same thing.
:
* '''''Object-to-Object Quantity Pattern'''''. When the quantity refers to a relationship between two objects, we use the reserved word "-to-" and the pattern: (object + "-to-" + object + quantity). The reserved word "-to-" can also be used for ratios. See the Ratio template. Examples include:

bear_brain-to-body__mass_ratio
earth-to-mars__travel_time
earth-to-sun__mean_distance

: When two objects are required to define a quantity, the last 2 objects in the object part of the name are often used, as in:

carbon_hydrogen__bond_length
hydrogen_oxygen__bond_energy (See: [http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html Table of bond energies].)

: In the last two examples, we put the two object names in alphabetical order to avoid two standard names for the same thing.
:
:We may also be able to use this pattern in constructions like: "land_subsurface-to-surface_water + seepage_rate", or "land_subsurface_water-to-surface + seepage_rate" or "ground_water-to-surface_water + seepage_rate" or "land_subsurface-to-land_surface_water + seepage_rate".
:
* '''''Object-or-Object Quantity Pattern'''''. In some cases, a quantity may apply to either of two alternate objects, as in:

land-or-sea_surface_radiation~incoming~shortwave__energy_flux

* '''''Quantity-to-Quantity Pattern'''''. Although similar to the Object-to-object Quantity Pattern, this pattern is used when two quantities (measured on the same object) are needed to define a new quantity as in:

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio [http://en.wikipedia.org/wiki/Charge-to-mass_ratio charge to mass ratio]
electron__mass-to-charge_ratio

:Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_x-section" + "wetted-area-to-perimeter_ratio".
:
* '''''Short Quantity Name Synonyms'''''. There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect = azimuth_angle_of_antigradient_of_elevation (relative to a fixed axis)
density = mass-to-volume_ratio (but density sometimes has other meanings; use "mass_density" ??)
discharge = water~outgoing + volume_flow_rate
slope = magnitude_of_gradient_of_elevation
speed = magnitude_of_velocity (or even "motion_rate"; process_name + quantity)
:
* '''''Incoming and Outgoing Quantity Rule'''''. Fluxes, flows and vector quantities may either enter or exit a given object (viewed as a control volume). In these cases, it is therefore necessary to distinguish between "incoming" or "outgoing". As of 7/23/14, "incoming" and "outgoing" are used as standard adjectives in such cases, even though it is also possible to use the Process Name + Quantity Pattern and then choose a process name that indicates whether the quantity is "incoming" or "outgoing". As of 8/16/14, the adjectives "incoming" and "outgoing" (with hyphens) may be applied to the transported substance in the object part of the name. Examples include:

atmosphere_top_surface_radiation~incoming~longwave__energy_flux
atmosphere_top_surface_radiation~incoming~shortwave__energy_flux
lake_water~incoming__volume_flow_rate
lake_water~outgoing__volume_flow_rate
model_grid_cell_water~incoming__volume_flow_rate
model_grid_cell_water~outgoing__volume_flow_rate
:
:Recall that "discharge" is a short synonym for "outgoing_volume_flow_rate". (The word "discharge" connotes an "outflow".) Note that "inflow" and "outflow" are valid process names. See the Discharge template.
:
:Note: In the CF Standard Names, "incoming" is only used in one name (namely, "toa_incoming_shortwave_flux") while "outgoing" is used in only 6 names (always containing "toa_outgoing_longwave_flux" or "toa_outgoing_shortwave_flux"). Recall that "toa" = "top_of_atmosphere".

 

== {{ Bar Heading| text=Absorptance}} ==

  base_quantity = "absorptance" 
  ''Examples of Specific Quantities:'' 
  "spectral_absorptance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__absorptance

* Absorptance (also called "absorptivity" and "absorption factor") is the dimensionless ratio of the radiation intensity absorbed by something to the original, incident radiation intensity. It is a number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* At a given wavelength, absorptance = emittance.
:
* The quantity "spectral absorptance" is the absorptance associated with a specific wavelength.
:
* The term '''absorbance''', although similar, is a different quantity that involves a log function.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Affinity}} ==

  base_quantity = "affinity" 
  ''Examples of Specific Quantities:'' 
  "chemical_affinity" 
  "electron_affinity" (of an atom or molecule)

  ''Examples''
chlorine_electron__affinity
magnesium-chloride_water__chemical_affinity
sulphuric-acid_water__chemical_affinity
water_electron__affinity

* Chemical affinity is defined in terms of [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy]. It is a quantity associated with two chemical species (atoms, molecules, ions, etc.) and therefore uses the '''Object-to-object Quantity Pattern'''.
:
* See [http://en.wikipedia.org/wiki/Chemical_affinity Chemical affinity], [http://en.wikipedia.org/wiki/Electron_affinity Electron affinity] and [http://en.wikipedia.org/wiki/Desiccant Desiccant].

 


== {{ Bar Heading| text=Age}} ==

  base_quantity = "age" 
  ''Examples of Specific Quantities:'' 
  "deposition_age"

  ''Examples''
sea_bottom_sediment__deposition_age

* The quantity '''age''' indicates the elapsed time since something was first formed or created, whether it be sea ice, a person or a sediment deposit. It has units of time.
:
* Note that "deposition_age" follows the Process Name + Base Quantity Name Pattern.
:
* See Duration and Time.

 


== {{ Bar Heading| text=Albedo}} ==

  base_quantity = "albedo" 
  ''Examples of Specific Quantities:'' 
  "black-sky_albedo" 
  "blue-sky_albedo" 
  "bond_albedo" 
  "geometric_albedo" 
  "visual_geometric_albedo" 
  "white-sky_albedo"

  ''Examples''
earth__bond_albedo
land_surface__albedo

* Albedo (also called "reflection coefficient") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface). The word albedo comes from the Latin word for "whiteness".
:
* '''Reflectance''' is a very closely related concept but there does not appear to be a universally accepted distinction between albedo and reflectance. Some authors take them to be equivalent, others use albedo for an average over shortwave radiation and reflectance as a function of wavelength, others describe albedo as either "diffuse reflectance" or "broadband reflectance" etc.. Dingman (2002) in his book Physical Hydrology defines albedo as the average of reflectance over visible wavelengths. This ambiguity was already recognized in a 1917 paper by Louis Bell. There have been recent efforts by Schaepman-Strub (2006) and others to standardize the terminology in descriptions of satellite surface albedo products. See Reflectance below.
:
* There is an important distinction between [http://en.wikipedia.org/wiki/Bond_albedo '''Bond albedo'''] and [http://en.wikipedia.org/wiki/Geometric_albedo '''Geometric albedo'''], and a formula relating the two. Bond albedos are strictly between 0 and 1 while geometric albedos can be greater than 1. (Enceladus, a large moon of Saturn, reportedly has a bond albedo of 0.99 and a visual geometric albedo of 1.4.) Bond albedo takes all wavelengths and phase angles of electromagnetic radiation into account.
:
* To more accurately characterize the scattering properties of a surface, a [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF) is often used. The integral of the BRDF over all viewing angles is called the [http://en.wikipedia.org/wiki/Directional-hemispherical_reflectance Directional-hemispherical reflectance] (DHR) or "black-sky albedo". There are two types of [http://en.wikipedia.org/wiki/Bi-hemispherical_reflectance Bi-hemispherical reflectance] (BHR). The first is often called "blue-sky albedo" (or "actual albedo"). The second -- often called "white-sky albedo" -- is the BHR under isotropic diffuse irradiance conditions (i.e. reflectance when there is only diffuse and no direct illumination, denoted as BHRiso). For many applications it is possible to approximate the albedo at a particular solar zenith angle as a linear combination of DHR (or black-sky albedo) and BHRiso (or white-sky albedo). The contribution from each is determined by D, the proportion of diffuse illumination. See: [http://en.wikipedia.org/wiki/Albedo#White-sky-and-black-sky_albedo White-sky and black-sky albedo].
:
* A '''Lambertian surface''' is an idealized model. In this sense it is similar to "black body", "channel centerline", "earth ellipsoid" or "mean-sea-level datum".
:
* See: [http://en.wikipedia.org/wiki/Albedo Albedo], [http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/albedo.html Albedo discussion], [http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function Bidirectional Reflectance Distribution Function] (BRDF), [http://en.wikipedia.org/wiki/Bond_albedo Bond albedo], [http://en.wikipedia.org/wiki/Geometric_albedo Geometric albedo], [http://en.wikipedia.org/wiki/Irradiance Irradiance], [http://en.wikipedia.org/wiki/Lambert%27s_cosine_law Lambert's cosine law], [http://en.wikipedia.org/wiki/Lambertian_reflectance Lambertian reflectance] and [http://en.wikipedia.org/wiki/Reflectivity Reflectance].

 


== {{ Bar Heading| text=Altitude}} ==

  base_quantity = "altitude"

  ''Examples''
airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude
submarine_above-seafloor__altitude (need "seafloor" vs. "bottom" for clarity here)

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* A skydiver or aircraft pilot is interested in knowing their height above the ground, locally, especially with regard to landing. Barometric altimeters (or pressure altimeters) measure the distance above mean sea level (so elevation), but may then be corrected using a QFE setting so that they display an altitude of zero for a given airfield (regardless of its elevation above sea level). Radar and laser altimeters measure the height above the ground directly by measuring the time it takes for a signal to reflect from the land surface and return to the aircraft.
:
* The standard sport skydiving altitude is 12,500 feet AGL (Above Ground Level); sometimes up to 18,000 feet AGL.
:
* Can we also use "altitude" for the height of an object (e.g. particle, submarine) above the sea floor (i.e. height above seafloor)? Do we need an extra adjective, like "bathymetric_altitude" or "above-bottom_altitude" ? We could also use something like "particle-to-bottom" + "distance" or just "particle_bottom_distance". The current approach is to use "above-bottom" as a "place" or "part", in the '''object part''' of the name.
:
* The standard term "equilibrium line altitude" (ELA) is discussed in the Attributes of Glaciers template.
:
* Note that in the CF Standard Names, "altitude" is used as a synonym for "elevation".
:
* See: [http://en.wikipedia.org/wiki/Altitude_above_ground_level Altitude above ground level], [http://en.wikipedia.org/wiki/Elevation Elevation], [http://en.wikipedia.org/wiki/Height_above_average_terrain Height above average terrain] (HAAT), [http://en.wikipedia.org/wiki/Lowest_safe_altitude Lowest safe altitude] and [http://en.wikipedia.org/wiki/Sea_level Mean sea level].
:
* See the Elevation template.

 


== {{ Bar Heading| text=Amplitude}} ==

  base_quantity = "amplitude"

  ''Examples''
sea_surface_water_wave__amplitude # wave~gravity
wave~airy__amplitude
wave~cnoidal__amplitude
wave~electromagnetic__amplitude
wave~seismic__amplitude
wave~stokes__amplitude

* "Amplitude" is a basic property of a periodic function or waveform, along with wavelength and wavenumber.

 


== {{ Bar Heading| text=Angle}} ==

  base_quantity = "angle"

  ''Examples''
azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle, depression_angle, dihedral_angle,
elevation_angle, exterior_angle, flare_angle, friction_angle, incidence_angle, inclination_angle, look_angle, nadir_angle,
phase_angle, pitch_angle, polarization_angle, rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle,
shock_angle, slope_angle, solid_angle, spreading_angle, tilt_angle, torsion_angle, vertex_angle,
yaw_angle, zenith_angle

* The local [http://en.wikipedia.org/wiki/Azimuth '''azimuth angle'''], [http://en.wikipedia.org/wiki/Zenith '''zenith angle'''], and '''elevation angle''' (the complement of the zenith angle, less often called "altitude angle") that can be associated with a 2D or 3D vector field are treated as operations in the CSDMS Standard Names. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates''']] for more information.
:
* There are two major conventions used for measuring angles. For '''bearings''', the angle is usually measured '''''clockwise from north''''', and this typically includes wind data. (We also need to clarify whether the wind is blowing "to" or "from" that direction.) Most other angles are measured the way you learned in high school, '''''counterclockwise from the x-axis''''' (or from the east). It is therefore important to specify the convention that is used. This can be done by including the appropriate <assume> tag in a model's Model Metadata File, chosen from the standardized assumption names on the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page. A smart framework would be able to convert between these two conventions, when necessary, after examining these <assume> tags. '''Note:''' We could also introduce "bearing" as another base quantity so that the metadata wouldn't be necessary.
:
* A '''bearing''' (to an observed object) can also be specified relative to the direction of travel of a vehicle (e.g. truck, ship or airplane) instead of relative to north. See: [http://en.wikipedia.org/wiki/Bearing_(navigation) Bearing (navigation)].
:
* A '''heading''' is the direction (usually given as a bearing) in which an object, such as a ship or airplane, is traveling. It is related to the '''course''' and '''track angle'''; see: [http://en.wikipedia.org/wiki/Course_(navigation) Course (navigation)].
:
* Note that "earth_axis" + "tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth ('''Part of Another Object Pattern''') and the quantity name "tilt_angle" follows the '''Process_name + Quantity Pattern'''. We use "tilt" vs. "tilting" as allowed by one of the Basic Rules. We use "earth_axis__tilt_angle" vs. "earth" + "axial_tilt_angle" in accordance with the '''Object vs. Adjective Rule'''.
:
* In the context of a satellite or airplane viewing the Earth's surface, the terms '''look angle''' and '''nadir angle''' are used to indicate the angle between straight down from the satellite (i.e. the nadir direction) and the ray that points from the satellite to a location on the Earth's surface. The complement of the "look angle" is often called the '''depression angle'''. The term "off-nadir angle" would be more descriptive but is not as widely used. "Zenith angle" and "elevation angle" are also complementary angles, typically used for a viewer on Earth's surface looking up at an object in the sky (e.g. the sun or a planet). '''Note''': The terms "view angle" or [http://en.wikipedia.org/wiki/Viewing_angle "viewing angle"] should not be used in this context because they have other, more common meanings related to a camera's "angle of view" or the angles from which a TV or monitor are being viewed.
:
* In the CSDMS Standard Names, the quantities "azimuth_angle_of_position_vector", "elevation_angle_of_position_vector" and "zenith_angle_of_position_vector" are used for an object viewed from the Earth's surface (e.g. satellite), while "azimuth_angle_of_look_vector", "depression_angle_of_look_vector", "nadir_angle_of_look_vector" are used for objects on the Earth's surface viewed from above (e.g. a satellite).
:
* The quantity [http://en.wikipedia.org/wiki/Angle_of_repose '''angle_of_repose'''] is called "repose_angle" in the CSDMS Standard Names. This may sound a bit strange when spoken, but this is outweighed by the benefits of following a standardized pattern.
:
* Many of these follow the '''Process_name + Quantity Pattern'''.
:
* CSDMS standard names use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle".
:
* bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.
:
* In the context of wheeled vehicles, several angles are used such as: [http://en.wikipedia.org/wiki/Camber_angle Camber angle] and [http://en.wikipedia.org/wiki/Caster_angle Caster angle] (or Rake angle).
:
* Three [http://en.wikipedia.org/wiki/Euler_angles Euler angles] can be used to describe the orientation of a rigid body, but different conventions are used. These would have some adjective(s) inserted before "euler_angle".
:
* The term [http://en.wikipedia.org/wiki/Flare_(ship) '''flare angle'''] refers to an angle measured from the vertical or main axis. The verb "flare" means to gradually become wider. (e.g. bell-bottom pants) The term "spreading_angle" is very similar.
:
* See: [http://en.wikipedia.org/wiki/Azimuth Azimuth angle], [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect (geography)], [http://en.wikipedia.org/wiki/Orbital_inclination Orbital inclination], [http://en.wikipedia.org/wiki/Slope Slope], [http://en.wikipedia.org/wiki/Solid_angle Solid angle] and [http://en.wikipedia.org/wiki/Zenith Zenith angle].

 


== {{ Bar Heading| text=Anomaly}} ==

  operation_prefix = "anomaly_of"

  ''Examples''
atmosphere_air__anomaly_of_pressure (i.e. difference from climatology)
atmosphere_air__anomaly_of_temperature
sea_surface_water__anomaly_of_geopotential_height
sea_surface_water__anomaly_of_temperature

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". It does not change the units. See Component, Increment and Magnitude.
:
* Means the "difference from climatology" in CF Standard Names. The "mean climatology" used as a reference should be specified in the Model Metadata File with an <assume> tag. See Reference Quantities.
:
* The word "anomaly" is used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

 


== {{ Bar Heading| text=Area}} ==

  base_quantity = "area" 
  ''Examples of Specific Quantities:'' 
  "surface_area"

  ''Examples''
basin_outlet__total_contributing_area
channel_x-section__area
glacier_surface__area
lake_surface__area
sphere_surface__area

* This quantity can be defined for any polygon and has units of length squared.
:
* The quantity "surface_area" can be defined for a surface that lies above some planar domain. However, this is usually not what is meant by the term "area". For CSDMS Standard Names, use "surface_area" for this situation and "area" otherwise.
:
* Several different terms are used for the area of a drainage basin, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A drainage basin can be viewed as a polygon with a well-defined area. The terms "total contributing area" (TCA) and "specific contributing area" (SCA) are used in reference to the region that contributes flow to an arbitrary line segment placed perpendicular to the flow direction at some point in a landscape. SCA is then defined as TCA divided by the length of this segment.
:
* When "surface" is used in connection with a body of water or ice, it indicates the top of that body and the area is the map view area.

 


== {{ Bar Heading| text=Aspect}} ==

  base_quantity = "angle" 
  ''Examples of Specific Quantities:'' 
  "aspect_angle"

  ''Examples''
land_surface__aspect_angle

* "Aspect angle" is the azimuth angle of the '''opposite''' of the gradient vector of elevation. Recall that the gradient is a 2D vector that points in the direction of '''''steepest downhill''''' and which has a magnitude equal to the slope. (See slope). The opposite of the gradient vector is a vector that points in the opposite direction, or the the direction of '''''steepest uphill'''''. It is sometimes referred to as the '''antigradient'''. Aspect angle could therefore also be expressed as: "azimuth_angle_of_antigradient_of_elevation".
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Capacity}} ==

  base_quantity = "capacity" 
  ''Examples of Specific Quantities:'' 
  "anion_exchange_capacity" (used in soil physics) 
  "cargo_capacity" (e.g. of an automobile) 
  "cation_exchange_capacity" (used in soil physics) 
  "carrying_capacity" (of an ecosystem) 
  "infiltration_capacity" ####### (in hydrology; also called "infiltrability") 
  "interception_capacity" (in hydrology) 
  "isobaric_heat_capacity" (constant pressure) (of an entire object, extensive) 
  "isochoric_heat_capacity" (constant volume) (of an entire object, extensive) 
  "mass-specific_isobaric_heat_capacity" (constant pressure) 
  "mass-specific_isochoric_heat_capacity" (constant volume) 
  "volume-specific_isobaric_heat_capacity" (constant pressure) 
  "volume-specific_isochoric_heat_capacity" (constant volume) 

  ''Examples''
air__volume-specific_isochoric_heat_capacity
anvil__isobaric_heat_capacity
aluminum__mass-specific_isobaric_heat_capacity
earth_human__carrying_capacity (need to specify two objects)
space-shuttle_tile__isochoric_heat_capacity

* The word "capacity" indicates the maximum "amount" of something that an object can hold. When applied to an empty container, like a fuel tank, it has units of volume. However, it may also be a nonnegative integer, as in "carrying capacity" or have other units, as in various types of heat capacity.
:
* [http://en.wikipedia.org/wiki/Heat_capacity '''Heat capacity'''] is an extensive property of an object (or matter); it is proportional to the amount of matter and can be used for discrete objects (like an anvil). There are two types of heat capacity, one computed with the pressure held constant, called "isobaric" and another with the volume held constant, called "isochoric". "Specific heat capacity" (often called "specific heat capacity") is an intensive property, that is, an amount per unit mass or volume. In the CSDMS Standard Names, the adjectives "mass-specific", "volume-specific" and "mole-specific" are used to remove ambiguity.
:
* "Thermal capacity" is another, but less commonly used term for "heat capacity".
:
* Aluminum, copper, cast iron and stainless steel cookware are often compared in terms of their thermal conductivity (how well they conduct heat) and heat capacity (how well they retain heat). See: [http://en.wikipedia.org/wiki/Cookware-and-bakeware Cookware and bakeware].
:
* The term [http://en.wikipedia.org/wiki/Carrying_capacity '''carrying capacity'''] follows the '''Process_name + Quantity Pattern''' and is the maximum population size for a given ecosystem.
:
* There are 4 CF Standard Names that contain "capacity", namely "soil_thermal_capacity" and 3 others that contain the phrase "at_field_capacity" and refer to soil moisture. The coresponding CSDMS standard name is: "soil_field_capacity_water_content". See the Soil template on the [[CSN_Object_Templates | '''CSDMS Object Templates''']] page for more information.
:
* See: [http://en.wikipedia.org/wiki/Battery_capacity#Battery_capacity-and-discharging Battery capacity], [http://en.wikipedia.org/wiki/Cation-exchange_capacity Cation-exchange capacity], [http://en.wikipedia.org/wiki/Channel_capacity Channel capacity], [http://en.wikipedia.org/wiki/Combining_capacity Combining capacity], [http://en.wikipedia.org/wiki/Heat_capacity Heat capacity] and [http://en.wikipedia.org/wiki/Tonnage Tonnage].

 


== {{ Bar Heading| text=Charge}} ==

  base_quantity = "charge" [C = Coulombs, SI unit]

  ''Examples''
electron__electric_charge

* The total electric charge is a fundamental conserved quantity of an isolated system.
:
* Electric charge is ''quantized'', that is, it comes in multiples of the the charge of an electron, called the ''elementary charge'', denoted as "e". The charge of a quark is 1/3 of this value. Electric charge also carries a sign; protons and electrons have charges of e and -e.
:
* See: [http://en.wikipedia.org/wiki/Electric_charge Electric charge] and [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge].

 

== {{ Bar Heading| text=Circulation}} ==

  base_quantity = "circulation"

  ''Examples''
airfoil_curve~enclosing__circulation

* In fluid dynamics, circulation is the line integral of a velocity field around a closed curve. If not otherwise specified, that closed curve is taken to enclose the object in the object part of the name (i.e. in a CSDMS Standard Name). The closed curve is also assumed to lie wholly within the "potential flow" region and not in the boundary layer close to the boundary of the airfoil/object.
:
* We could also use something like: "airfoil" + "closed_line_integral_of_velocity"
:
* See: [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation].

 


== {{ Bar Heading| text=Code}} ==

  base_quantity = "code"

  ''Examples''
basin__pfafstetter_code
basin__usgs_hydrologic_unit_code
location__postal_code (See: [http://en.wikipedia.org/wiki/Postal_code Postal code].)

* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used.
:
* Codes sometimes include both numbers and letters.
:
* See Number.

 


== {{ Bar Heading| text=Coefficient}} ==

  base_quantity = "coefficient" 
  ''Examples of Specific Quantities:'' 
  "absorption_coefficient" 
  "attenuation_coefficient" 
  "diffusion_coefficient" 
  "drag_coefficient" 
  "eddy_diffusion_coefficient" 
  "exchange_coefficient" 
  "expansion_coefficient" 
  "extinction_coefficient" 
  "friction_coefficient" 
  "lift_coefficient" 
  "partition_coefficient" 
  "reaeration_coefficient" 
  "reflection_coefficient" 
  "scattering_coefficient" 
  "sieving_coefficient" 
  "transfer_coefficient" 
  "transmission_coefficient"

  ''Examples''
airfoil__drag_coefficient
airfoil__lift_coefficient
concrete_rubber__kinetic_friction_coefficient
atmosphere_air_radiation__beer_lambert_law_attenuation_coefficient
iron__thermal_volume_expansion_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient (See Constants in Math)
pavement_rubber__static_friction_coefficient
polynomial__leading_coefficient
spring~steel__hooke_law_coefficient [kg s-2] (the "spring constant" in Hooke's law)
water_salt__diffusion_coefficient

* Coefficients are '''multiplicative factors''' that often occur in empirical laws, and other mathematical expressions. In the CSDMS Standard Names, other "control variables" that do not appear as multiplicative factors are referred to as '''parameters'''. (However, sometimes people refer to these other parameters as coefficients.) Coefficients and exponents can be viewed as special types of parameters. [http://en.wikipedia.org/wiki/Parameter '''Parameters'''] are typically not model state variables, but instead are "tunable" "control parameters" that define the model itself.
:
* Many quantity names (see above) are built from the base quantity "coefficient" and a process name, which conforms to the '''Process_name + Quantity Pattern'''.
:
* [http://en.wikipedia.org/wiki/Diffusion '''Diffusion'''] is the process by which a substance moves (down gradient) from regions of high concentration to regions of low concentration. In [http://en.wikipedia.org/wiki/Molecular_diffusion '''molecular diffusion'''] this process is driven by thermal energy. In [http://en.wikipedia.org/wiki/Turbulent_diffusion '''turbulent diffusion'''] it is driven by random fluctuations and swirling structures in the flow, such as eddies. When unqualified, a diffusion coefficient refers to the parameter, D, in the [http://en.wikipedia.org/wiki/Diffusion_equation diffusion equation] that has units of [m2 s-1], regardless of what substance is diffusing. The term [http://en.wikipedia.org/wiki/Eddy_diffusion '''eddy diffusion coefficient'''] (also called "eddy diffusivity") is used for turbulent diffusion and also has units of [m2 s-1]. See the section for Diffusivity (which needs to be reconciled with this one).
:
* The concept of '''bulk parameterization''' is used in atmosphere and ocean science in order to estimate the rates (as fluxes) at which mass, momentum and heat are transferred between the atmosphere and the surface of either the land or sea. This approach uses the logarithmic law of the wall to relate the fluxes to values of heat, momentum, humidity (water vapor) or other gases that are measured at some fixed height above the interface (e.g. 10 meters). The use of the adjective "bulk" seems to stem partly from the idea of "bulk flow" (also called "free stream flow"), or flow that is far enough away from the interface boundary that it moves relatively unimpeded, as opposed to near-boundary flow. It also indicates that fluxes obtained by this method should be applicable over larger areas. '''Bulk transfer coefficients''' (also called "bulk exchange coefficients") are quantities associated with this approach, and can be defined somewhat differently by different authors, for example as dimensionless quantities or including shear velocity as a factor (with velocity units). There are separate bulk transfer coefficients for mass (water vapor or another gas, which may condense at the interface), momentum and heat. These bulk transfer coefficients are initially computed for a "neutral" state (e.g. when the surface temperature is equal to the air temperature), and then typically adjusted (e.g. by a function of bulk Richardson number) depending on whether the (stratified) atmosphere is in a "stable" (e.g. T_surf > T_air) or "unstable" (T_surf < T_air) state. These considerations lead to standard names such as "bulk_mass_transfer_coefficient" and "bulk_sensible_heat_transfer_coefficient" which are taken to be dimensionless. Note that the adjectives "stable" and "unstable" are not included because they are attributes of the atmosphere that are used to compute the bulk transfer coefficient but can change during a model run. The adjective "neutral" can be included, however, since this allows access to the "base value" that is modified for the stable and unstable cases. '''Note''': The product of the wind speed at the reference height and a bulk transfer coefficient is sometimes called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal is then the "bulk aerodynamic resistance".
:
* In the book, "Hydrology: An Introduction" by Brutsaert (2005, p. 41), the transfer coefficients for mass, momentum and heat are defined as dimensionless numbers and denoted as: Ce, Cd and Ch. Ce is also called the Dalton number (for water vapor). Cd is also called the [http://en.wikipedia.org/wiki/Drag_coefficient '''drag coefficient''']. Ch is also called the [http://en.wikipedia.org/wiki/Stanton_number '''Stanton number''']. However, this differs from other definitions; see: [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient] (SI units of [W m-2 K-1]) and [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient] (SI units of [m s-1]).
:
* The "Manning n parameter" is sometimes called "Manning's roughness coefficient" or "Manning's coefficient" or something similar. (But the word "roughness" is not needed to remove ambiguity.) Since Manning's n appears in the denominator of Manning's formula, it technically isn't a coefficient (i.e. its inverse is the multiplicative factor, or coefficient). Note that [http://en.wikipedia.org/wiki/Manning_formula Manning's formula] also contains another parameter, usually denoted by "k" that serves as a unit conversion factor. In the CSDMS Standard Names these are both referred to as "parameters" and use that pattern.
:
* The terms "attenuation_coefficient" and "attenuation_factor" are both used but they refer to different quantities associated with the '''Beer-Lambert Law'''. The "attenuation coefficient" is a parameter in the Beer-Lambert law with units of inverse length. When applied to gases in the atmosphere, dimensionless quantities called "optical air mass" and "optical depth" are instead used in the exponential. "Attenuation factor " is apparently a synonym for "transmittance", which is the ratio of transmitted to incident radiation, I(x)/I(0), a positive number less than 1. See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Airmass Air mass], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert Law], [http://en.wikipedia.org/wiki/Optical_depth Optical depth] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].
:
* See: [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Ballistic_coefficient Ballistic coefficient], [http://en.wikipedia.org/wiki/Binomial_coefficient Binomial coefficient], [http://en.wikipedia.org/wiki/Coefficient Coefficient], [http://en.wikipedia.org/wiki/Drag_coefficient Drag coefficient], [http://en.wikipedia.org/wiki/Extinction_coefficient Extinction coefficient], [http://en.wikipedia.org/wiki/Friction Friction], [http://en.wikipedia.org/wiki/Heat_transfer_coefficient Heat transfer coefficient], [http://en.wikipedia.org/wiki/Lift_coefficient Lift coefficient], [http://en.wikipedia.org/wiki/Manning_formula Manning formula], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Mass_transfer_coefficient Mass transfer coefficient], [http://en.wikipedia.org/wiki/Partition_Coefficient Partition coefficient], [http://en.wikipedia.org/wiki/Pressure_coefficient Pressure coefficient], [http://en.wikipedia.org/wiki/Reflection_coefficient Reflection coefficient], [http://en.wikipedia.org/wiki/Sieving_coefficient Sieving coefficient], [http://en.wikipedia.org/wiki/Skin_friction#Skin_friction Skin friction coefficient], [http://en.wikipedia.org/wiki/Thermal_expansion Thermal expansion] and [http://en.wikipedia.org/wiki/Transmission_coefficient_(physics) Transmission coefficient].
:
* See Constant, Exponent, Factor, Index, Number and Parameter.
:
* See Friction.

 


== {{ Bar Heading| text=Component}} ==

  [ direction adjective(s) ] + "_component_of_" + [ vector quantity ]

  ''Examples''
atmosphere_air_flow__east_component_of_velocity
atmosphere_air_flow__north_component_of_vorticity
channel_water_flow__x_component_of_velocity
sea_water_flow__down_east_component_of_stress

* Components of vectors and tensors are constructed using coordinate-direction adjectives and the "component_of" operation, as shown in the examples above.
:
* The coordinate-direction adjectives are: east, west, north, south, x, y, z, up, down, offshore, longshore, cross_stream and downstream. Two coordinate-direction adjectives are needed for a component of "flow_shear_stress". As of 7/28/14, eastward, westward, northward and southward have been shortened to east, west, north and south.
:
* Note that the word "flow" is used in the object part of the name as a shorthand for "flow_field". It is another example of the Object Name + Model Name Pattern.
:
* See Stress, Velocity and Vorticity.
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 

== {{ Bar Heading| text=Compressibility}} ==

  base_quantity = "compressibility" 
  ''Examples of Specific Quantities:'' 
  "isentropic_compressibility" 
  "isothermal_compressibility"

  ''Examples''
atmosphere_air__isothermal_compressibility

* Compressibility is a measure of the relative change in volume in response to a pressure.
:
* See: [http://en.wikipedia.org/wiki/Compressibility Compressibility] and [http://en.wikipedia.org/wiki/Compressibility_equation Compressibility equation].

 


== {{ Bar Heading| text=Concentration}} ==

  base_quantity = "concentration" 
  ''Examples of Specific Quantities:'' 
  "mass_concentration" [kg m-3] 
  "molar_concentration" [mol m-3] (molarity) 
  "number_concentration" [m-3] 
  "volume_concentration" [1] = [m3 / m3]

  ''Examples''
channel_water_sediment~suspended__mass_concentration
sea_water_magnesium-chloride__molar_concentration
sea_water_sediment~suspended__mass_concentration

* There are four main types of concentration, shown above, and they all have different units.
:
* The quantity "concentration" is always associated with two substances (objects) so we use the '''Object-in-object Quantity Pattern'''.
:
* '''''Molality''''' is a related concept with SI units of [mol kg-1].
:
* '''''Mass fraction''''' and '''''mole fraction''''' are both dimensionless ratios.
:
* '''''Mass ratio''''' and '''''mole ratio''''' are also dimensionless ratios and are considered "mixing ratios". See: [http://en.wikipedia.org/wiki/Mixing_ratio Mixing ratio].
:
* "Molar concentration" is also called "molarity". See: [http://en.wikipedia.org/wiki/Molarity Molarity].
:
* "Volume concentration" is also called "volume fraction". See Fraction.
:
* The term "osmotic concentration" is also used.
:
* See: [http://www.stanford.edu/group/Urchin/mineral.html "Mineral makeup of seawater"].
:
* See: [http://en.wikipedia.org/wiki/Concentration Concentration], [http://en.wikipedia.org/wiki/Seawater Seawater] and [http://en.wikipedia.org/wiki/Sediment_transport Sediment transport].

 


== {{ Bar Heading| text=Conductance}} ==

  base_quantity = "conductance" 
  ''Examples of Specific Quantities:'' 
  "atmospheric_conductance" [m s-1] 
  "bulk_atmospheric_conductance" [m s-1] 
  "electrical_conductance" [A V-1] 
  "fluid_conductance" [m2 s-1] 
  "thermal_conductance"

  ''Examples''
snow__thermal_conductance

* Conductance is the reciprocal of resistance.
:
* Conductance is different from conductivity. See Conductivity.
:
* The product of wind speed at a reference height and a bulk transfer coefficient is called the "bulk aerodynamic conductance" (of mass, momentum or heat). The reciprocal, "bulk aerodynamic resistance", is also used. See Coefficient.
:
* Units cannot be determined from the "base quantity" name as shown above.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistance-and-conductance Electrical resistance and conductance], [http://en.wikipedia.org/wiki/Fluid_conductance Fluid conductance] and [http://en.wikipedia.org/wiki/Thermal_conductivity#Conductance Thermal conductance].

 


== {{ Bar Heading| text=Conductivity}} ==

  base_quantity = "conductivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_conductivity" [siemens m-1] or [ohm-1 m-1] 
  "hydraulic_conductivity" [m s-1] 
  "ionic_conductivity" 
  "molar_conductivity" 
  "thermal_conductivity" [W m-1 K-1] (this is an intensive property; don't need to add "specific")

  ''Examples''
sea_water__electrical_conductivity
snow__thermal_conductivity
soil__saturated_hydraulic_conductivity

* Units cannot be determined from the "base quantity" name as shown above.
:
* Hydraulic conductivity can depend on coordinate direction unless the soil is assumed to be isotropic. When applicable, include an <assume> tag in the Model Metadata File with the standard assumption name: "isotropic_medium". See [[CSN_Assumption_Names | CSDMS Assumption Names]] for more information.
:
* "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).
:
* See: [http://en.wikipedia.org/wiki/Electrical_conductivity Electrical conductivity], [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [https://en.wikipedia.org/wiki/Molar_conductivity Molar conductivity] and [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity].

 


== {{ Bar Heading| text=Constants in Math}} ==

  base_quantity = "constant" 
  "math_" + constant_name + "_constant"

  ''Examples''
math__catalan_constant
math__chaitin_constant
math__conway_constant
math__e_constant (or math_euler_e_constant ??)
math__euler_gamma_constant
math__feigenbaum_alpha_constant
math__feigenbaum_delta_constant
math__golden_ratio_constant
math__googol_constant
math__khinchin_constant
math__pythagoras_constant (= square root of 2)
math__sierpinski_constant
math__twin_prime_constant
math__pi_constant

* This includes numbers like "pi", "phi" and "e". See [http://en.wikipedia.org/wiki/Mathematical_constant Wikipedia: Mathematical constant] for a table with numerous examples.
:
* These numbers are not a quantity associated with an object like our others so we have used "math" as a placeholder object. Note that one model may want to check the number of significant digits of a math constant (like pi) that are used in another model, for example.
:
* phi = 1.61803... is known as the [http://en.wikipedia.org/wiki/Golden_ratio golden ratio].
:
* See the Dimensionless Number template.

 


== {{ Bar Heading| text=Constants in Physics}} ==

  base_quantity = "constant"

  ''Examples''
air__dielectric_constant [1] (can be complex)
earth__solar_constant [W m-2] (solar_irradiation_constant may be better)
earth__standard_gravity_constant [m s-2] ("little g", see Attributes of Planets template)

physics__atomic_mass_constant [kg] (about 1.660538921e-27)
physics__avogadro_constant [unit mol-1] (see Note below)
physics__bohr_radius_constant [m] (about 5.2917721092e-11)
physics__boltzmann_constant (See ideal_gas_constant)
physics__cosmological_constant [m-2] (about 10^{-52}; object = universe)
physics__coulomb_constant [N m2 C-2] (C = Coulomb SI unit)
physics__elementary_charge_constant [C] (charge of a proton and > 0; -1 times charge of an electron)
physics__fine_structure_constant [1] (about 1/137.035999074)
physics__first_radiation_constant [W m2] (for a black body)
physics__gravitational_coupling_constant [1] (about 1.7518e-45)
physics__hartree_energy_constant [J]
physics__ideal_gas_constant [J mol-1 K-1] (R = 8.3144621)
physics__planck_constant [J s] (h = 6.62606957e-34)
physics__planck_charge_constant [C] (about 1.875545956e-18)
physics__planck_length_constant [m] (about 1.616199e-35)
physics__planck_mass_constant [kg] (about 2.17651e-8)
physics__planck_temperature_constant [K] (about 1.416833e+32)
physics__planck_time_constant [s] (about 5.39106e-44)
physics__reduced_planck_constant
physics__rydberg_constant [m-1]
physics__second_radiation_constant [m K] (for a black body)
physics__stefan_boltzmann_constant [W m-2 K-4]
physics__universal_gravitation_constant [m3 kg-1 s-2] ("big G", from Newton's law; or just "gravitational_constant")
physics__vacuum_electric_permittivity_constant [F/m] (also called "electric constant")
physics__vacuum_impedance_constant [ohms] (about 376.73031)
physics__vacuum_light_speed_constant [m s-1] (put "vacuum" in the object part ??) ##########
physics__vacuum_magnetic_permeability_constant [N A-2] or [H m-1] (also called "magnetic constant")
physics__von_karman_constant [1]

* If there is no naturally-associated object, the object name "physics" can be used as a placeholder object name. In some cases we could use "universe" or "vacuum" as the object name.
:
* Although "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they have the following CSDMS standard names:
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])
:Note that "specific_latent_heat" is a quantity name so the quantity name part of these examples conforms to the '''Process_name + Quantity Pattern'''. See the template for Heat and [http://en.wikipedia.org/wiki/Latent_heat Latent heat].
:
* The modern name for "Avogadro's number" is the "avogadro_constant". (See [http://en.wikipedia.org/wiki/Avogadro_constant Avogadro constant].) It has units and is equal to: 6.02214129(27)x10^{23} [mol-1] or [unit mol-1]
:
* The speed of light depends on the medium it is traveling through. In a vacuum, v = c = 299,792,458 [m s-1]. In other materials, v = (c / n), where n > 1 is the ''refraction index''. For visible light in air, n is about 1.0003. So an unambiguous standard name should indicate the medium and the wavelength range in the object name. Since the medium that the light is traveling through matters, we use the '''Object-in-object Quantity Pattern''' to create standard names such as: "visible_light_in_air_speed".
:
* The speed of light in a vacuum is a constant that is independent of wavelength. Perhaps we should give it the standard name "light_in_vacuum_speed_constant" which follows the '''Object-in-object Quantity Pattern'''.
:
* The "universal gravitational constant' appears in Newton's Law of Gravitation and is denoted as G (big G). It has units of [m3 kg-1 s-2]. The "Earth gravitational constant" is more correctly called the "Earth standard gravity constant". It is the average free-fall acceleration of Earth's gravitational field near the surface of the Earth and is denoted as g (little g). Even though it varies with position on Earth, it is defined to be precisely 9.80665 [m s-2] (an average value). See: [http://en.wikipedia.org/wiki/Standard_gravity Standard gravity] and [http://en.wikipedia.org/wiki/Gravity_of_Earth Gravity of Earth].
:
* While the coefficient in Hooke's law is often called the '''''spring constant''''', we instead use ''''spring~steel__hooke_law_coefficient''''' for consistency with coefficients in other empirical laws.
:
* In meteorology, the ratio of the ideal gas constant, R, and the isobaric mass-specific heat capacity, cp, is called the '''Poisson constant'''. It is used in the definition of potential temperature.
:
* See: [http://en.wikipedia.org/wiki/Boltzmann_constant Boltzmann constant], [http://en.wikipedia.org/wiki/Coulomb_constant Coulomb constant], [http://en.wikipedia.org/wiki/Elementary_charge Elementary charge], [http://en.wikipedia.org/wiki/Fine_structure_constant Fine-structure constant], [http://en.wikipedia.org/wiki/Gravitational_coupling_constant Gravitational coupling constant], [http://en.wikipedia.org/wiki/Gas_constant Ideal gas constant],[http://en.wikipedia.org/wiki/Planck_constant Planck constant], [http://en.wikipedia.org/wiki/Psychrometric_constant Psychrometric constant],[http://en.wikipedia.org/wiki/Rydberg_constant Rydberg constant], [http://en.wikipedia.org/wiki/Stefan–Boltzmann_constant Stefan-Boltzmann constant], [http://en.wikipedia.org/wiki/Gravitational_constant Universal gravitational constant], [http://en.wikipedia.org/wiki/Vacuum_permittivity Vacuum electric permittivity], [http://en.wikipedia.org/wiki/Vacuum_permeability Vacuum magnetic permeability] and [http://en.wikipedia.org/wiki/Von_Kármán_constant von Karman constant].
:
* See: [http://en.wikipedia.org/wiki/Physical_constant Physical constant].

 


== {{ Bar Heading| text=Content}} ==

  base_quantity = "content" 
  ''Examples of Specific Quantities:'' 
  "energy-per-area_cold_content" 
  "energy_content" 
  "mass_content" 
  "volume_content"

  ''Examples''
coal__thermal_energy_content
gasoline__thermal_energy_content
snowpack__energy-per-area_cold_content ? (See Note below.)
wood~dry__thermal_energy_content

* The word "content" refers to the "amount contained within". It is therefore naturally associated with two objects and the '''Object-in-object Quantity Pattern'''.
:
* In the CF Standard Names, the term "content" is taken to mean an "amount per unit area", usually determined as a z-integral from the bottom to the top of the atmosphere of a mass or volume fraction. (e.g. CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content".) However, in other contexts it means an amount per unit volume, as in the term "water_content" from infiltration theory, which is a volume fraction. See [http://en.wikipedia.org/wiki/Water_content Water Content].
:
* While soil "water content" is a fairly standard term in hydrology (infiltration theory), the CSDMS Standard Names use "volume_fraction" instead since it is less ambiguous, provides the definition, applies equally well to other objects like clay and sand, and keeps the word "water" in the object part of the name. See Attributes of Soil at [[CSN_Examples | CSDMS Standard Name Examples]]. However, it might be better to retain the word "content" for easy recognition (since "water content" is so widely used, and then use "volume_content" and "mass_content" instead of "volume_fraction" and "mass_fraction". Sometimes the terms ''gravimetric water content'' and ''volumetric water content'' are also used.
:
* The quantity "thermal_energy_content" is used in the context of fuels like coal, gas and wood, to indicate the amount of useful energy that can be extracted.
:
* The quantity "cold_content" is used in snow hydrology to describe the "energy deficit" that must be overcome before melting starts to occur. It is expressed as energy per unit area [J m-2]. This deficit results in an observed time lag between when the temperature is raised above the melting point to when snow actually begins to melt. It involves the concept of "latent heat of fusion" -- the (originally mysterious) amount of heat energy that must be added to a solid material before there is any change in its temperature. (See: [http://en.wikipedia.org/wiki/Latent_heat Latent heat]. In the CF Standard Names, the term "thermal_energy_content_of_surface_snow" is used, apparently to mean "cold_content". However, a Google search on "thermal energy content of snow" only returns 2 hits, and these are from the CF names. Note that "cold_content" is negative and "thermal_energy_content" is typically positive.
:
* Many [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] contain the base quantity "content". The following list shows the number, in parentheses, or each use pattern:

carbon_content [kg m-2] (14)
energy_content [J m-2] (25) e.g. "thermal_energy_content_of_surface_snow"
enthalpy_content [**********] (4)
heat_content [J m-2] (2)
ice_content [kg m-2] (2)
mass_content [kg m-2] (235)
moisture_content [kg m-2] or [m] (6)
number_content [m-2] (7)
ozone_content [Pa] or [m] (2)
soot_content [kg m-2] (1)
sulfate_content [kg m-2] (1)
vapor_content [kg m-2] (14) (most are "tendencies")
water_content [kg m-2] (16)

: We may therefore have a conflict with "water_content" unless it is resolved by the object part.

 


== {{ Bar Heading| text=Coordinate}} ==

  base_quantity = "coordinate"

  ''Examples''
alongshore_coordinate (oriented along and based on a shoreline; similar to sigma coordinates)
cross-shore_coordinate (off-shore and on-shore directions)

cross-stream_coordinate (oriented along and based on a stream centerline)
streamwise_coordinate (upstream and downstream directions)

east_coordinate (for a model; if not same as longitude)
west_coordinate
north_coordinate (for a model; if not same as latitude)
south_coordinate

r_coordinate (Cylindrical and Spherical coordinates, with azimuth_angle and elevation_angle)

u_coordinate (e.g. orthogonal curvilinear coordinate systems)
v_coordinate (e.g. orthogonal curvilinear coordinate systems)

x_coordinate (Cartesian coordinates)
y_coordinate (Cartesian coordinates)
z_coordinate (Cartesian coordinates)

* Note that Geographic coordinates use '''latitude''' (north-south coordinate), '''longitude''' (east-west coordinate) and '''elevation''' (vertical coordinate). These are treated as standard base quantity names in the CSDMS Standard Names. See: [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinates].
:
* For spherical coordinates, we would usually use "azimuth_angle" and "elevation_angle" instead of "theta_coordinate" and "phi_coordinate". But perhaps the latter should also be allowed.
:
* The terms "normal_coordinate" and "tangential_coordinate" are also used in some contexts.
:
* See: [http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy) Barycentric coordinates] (astronomy), [http://en.wikipedia.org/wiki/Barycentric_coordinate_system Barycentric coordinates] (for a triangle or other simplex), [http://en.wikipedia.org/wiki/Canonical_coordinates Canonical coordinates], [http://en.wikipedia.org/wiki/Coordinate_system Coordinate system], [http://en.wikipedia.org/wiki/Fermi_coordinates Fermi coordinates], [http://en.wikipedia.org/wiki/Fractional_coordinates Fractional coordinates] (crystallography), [http://en.wikipedia.org/wiki/Galilean_transformation Galilean transformation], [http://en.wikipedia.org/wiki/Generalized_coordinates Generalized coordinates], [http://en.wikipedia.org/wiki/Isothermal_coordinates Isothermal coordinates], [http://en.wikipedia.org/wiki/Normal_coordinates Normal coordinates] (from differential geometry) and [http://en.wikipedia.org/wiki/Sigma_coordinate_system Sigma coordinate system] (also called terrain-following).
:
* See the section for Components above, where the same prefixes are used. In fact, instead of using "coordinate" as a base quantity, it would be possible to use "position", which is a vector quantity, similar to velocity. Then we could use "x_component_of_position" instead of "x_coordinate", etc. just as we use "x_component_of_velocity". Note that while the components of a position vector are called "coordinates", there is no similar, short term for the components of a velocity vector.

 


== {{ Bar Heading| text=Correlation}} ==

  base_quantity = "correlation"

  ''Examples''
(None yet)

* Note that correlations require two quantities to be specified, which is similar to certain other quantities such as Partial Pressure and Solubility.
:
* Although the Guidelines for Constructing CF Standard Names includes a provision for correlations as the transformation pattern: "correlation_of_X-and-Y_over_Z", there are currently no examples of CF Standard Names that contain "correlation". The same is true for "covariance" and "convergence". There are only three names with "divergence".

 

== {{ Bar Heading| text=Count}} ==

  base_quantity = "count" 
  ''Examples of Related Quantities:'' 
  "number_concentration" (count per volume)

  ''Examples''
basin_rain-gauge__count
human_blood_cell~platelet__number_concentration [count / microliter]
human_blood_cell~red__number_concentration
human_blood_cell~white__number_concentration
lake_water_fish_sample__count
mars_moon__count
model_grid_column__count

* This quantity name is sometimes used when the attribute being quantified can only take non-negative integer values, as in the examples above. The word "count" is preferable to "number", since a "number" doesn't need to be an integer and is used as a root quantity for dimensionless numbers (e.g. Reynold's number). However, "count concentration" is not typically used, so we use "number concentration" in that case.
:
* In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: [http://en.wikipedia.org/wiki/Blood_cell_count Blood cell count]. Once units are specified (e.g. in a Model Coupling Metadata (MCM) file), then "number_concentration" is unambiguous. Is a platelet technically considered to be a type of blood cell?
:
* The "Wolman pebble count" due to [http://webapps.jhu.edu/jhuniverse/featured/reds_wolman/ M. Gordon "Reds" Wolman] is sometimes used in river hydraulics and sediment transport. However, the goal of this procedure is to estimate the mean diameter of the pebbles on the stream bed, so the actual "count" (usually 100) is not of primary interest.
:
* The "diatom count" of a sample may be another example; are the units then the same as "abundance"? (e.g. "sediment_core_diatom_relative_abundance" ?)
:
* The number of occurrences of a given event may also be called a "count". (e.g. Geiger counters)
:
* See [http://en.wikipedia.org/wiki/Count_data Count data] and the Number template.

 


== {{ Bar Heading| text=Current}} ==

  base_quantity = "current" 
  ''Examples of Specific Quantities:'' 
  "electrical_current"

  ''Examples''
None yet.

* An electric current is a flow of charge, with an SI unit of "amperes" (i.e. "coulombs per second").
:
* See: [http://en.wikipedia.org/wiki/Electric_current Electric current].

 


== {{ Bar Heading| text=Curvature}} ==
:
  base_quantity = "curvature" 
  ''Examples of Specific Quantities:'' 
  "gaussian_curvature" 
  "mean_curvature" 
  "max_normal_curvature" (a principle curvature) 
  "min_normal_curvature" (a principle curvature) 
  "plan_curvature" 
  "profile_curvature" 
  "streamline_curvature" 
  "tangential_curvature" 

  ''Examples''
land_surface__plan_curvature
land_surface__profile_curvature

* Curvatures can be defined for surfaces that are twice-differentiable. In reality, natural surfaces are rough but they can be approximated as twice-differentiable surfaces.
:
* Plan curvature (or "contour curvature"), profile curvature and streamline curvature are used in [http://en.wikipedia.org/wiki/Geomorphometry geomorphometry], the analysis of land surfaces or topography.
:
* See Attributes of Topography and Attributes of Oceans on the [[CSN_Examples | Examples]] page.
:
* Curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).
:
* See: [http://en.wikipedia.org/wiki/Curvature Curvature], [http://en.wikipedia.org/wiki/Geomorphometry Geomorphometry] and [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature].

 


== {{ Bar Heading| text=Density}} ==

  base_quantity = "density" 
  ''Examples of Specific Quantities:'' 
  "bits-per-area_density" 
  "bulk_mass-per-volume_density" 
  "charge-per-area_density" 
  "current-per-area_density" [A m-2] (known as "current density") 
  "energy-per-area_density" [J m-2] 
  "energy-per-volume_density" [J m-3] 
  "length-per-area_density" [m-1] 
  "mass-per-area_density" [kg m-2] 
  "mass-per-volume_density" [kg m-3] 
  "number-per-area_density" [m-2] 
  "number-per-volume_density" [m-3] 
  "particle_mass-per-volume_density" 
  "power-per-length_density" [W m-1] (used for ocean wave crests) 
  "power-per-area_density" [W m-2] (known as "surface power density") 
  "power-per-volume_density" [W m-3] 
  "torque-per-volume_density" [N m / m-3] = [N m-2]

  ''Examples''
atmosphere_air__mass-per-volume_density
atmosphere_air__mass-per-volume_density (stp = standard temperature and pressure)
basin_channels__total-length-per-area_density (known as "drainage_density")
universe~friedmann__critical_h-atom-per_volume_density
sea_water__mass-per-volume_density

* The word '''density''' usually refers to the amount of something within a fixed amount of space. The "amount of space" could be 1D (line), 2D (area) or 3D (volume). For greater clarity (and to avoid ambiguity), standard quantity names like ''mass-per-volume_density'' and the others listed above are used in the CSDMS Standard Names. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.
:
* The quantity name [http://en.wikipedia.org/wiki/Bulk_density '''Bulk density'''] refers to the mass of many particles (e.g. sediment grains) divided by the volume that they occupy. For clarity, here we use "bulk_mass-per-volume_density".
:
* [http://en.wikipedia.org/wiki/Area_density#Column_density Column density] is a type of area density defined as the z integral of a volume fraction from the bottom to the top of a column of water or air, as in the ocean or atmosphere. In the CF names, the quantity name "content" is used for this concept. In the context of sediment plumes, the quantity name "sediment inventory" is used for this concept (a z-integral over the depth of a freshwater plume entering the sea).
:
* Physicists sometimes use the term "flux_density".
:
* Hydrologists use the term "drainage_density", which is defined as the total length of channels in a drainage basin divided by the drainage area. Generic units are therefore inverse length. Similarly, "source_density" can refer to the total number of sources (i.e. channel heads) in a basin divided by the drainage area.
:
* Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".
:
* See: [http://en.wikipedia.org/wiki/Area_density Area density], [http://en.wikipedia.org/wiki/Area_density#Column_density Column density], [http://en.wikipedia.org/wiki/Bulk_density Bulk density], [http://en.wikipedia.org/wiki/Critical_density Critical density],[http://en.wikipedia.org/wiki/Current_density Current density], [http://en.wikipedia.org/wiki/Density Density], [http://en.wikipedia.org/wiki/Drainage_density Drainage density], [http://en.wikipedia.org/wiki/Electron_density Electron density], [http://en.wikipedia.org/wiki/Energy_density Energy density], [http://en.wikipedia.org/wiki/Knot_density Knot density], [http://en.wikipedia.org/wiki/Linear_density Linear density], [http://en.wikipedia.org/wiki/Memory_storage_density Memory storage density], [http://en.wikipedia.org/wiki/Number_density Number density], [http://en.wikipedia.org/wiki/Orthobaric_density Orthobaric density], [http://en.wikipedia.org/wiki/Particle_density Particle density], [http://en.wikipedia.org/wiki/Population_density Population density], [http://en.wikipedia.org/wiki/Potential_density Potential density], [http://en.wikipedia.org/wiki/Power_density Power density], [http://en.wikipedia.org/wiki/Probability_density_function Probability density function], [http://en.wikipedia.org/wiki/Relative_density Relative density], [http://en.wikipedia.org/wiki/Surface_power_density Surface power density], [http://en.wikipedia.org/wiki/Torque_density Torque density] and [http://en.wikipedia.org/wiki/Vapour_density Vapour density].

 


== {{ Bar Heading| text=Depth}} ==

  base_quantity = "depth" 
  ''Examples of Specific Quantities:'' 
  "secchi_depth"

  ''Examples''
channel_water__mean_depth
sea_water__secchi_depth
sea_water_below-surface__depth
sea_water_bottom__depth
soil_sat-zone_top__depth ##### (or if not soil, land_subsurface_sat-zone_top__depth).

* Measured as a positive downward distance below a reference surface. In this sense, it is the opposite of "height" which is measured positive upward from a reference surface.
:
* CF Standard Names often use "thickness" instead of "depth". See the template for Thickness.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum, and which may take values less than some maximum possible value.
:
* Note that "secchi_depth" is a standard term that measures turbidity using a "visible depth". See: [http://en.wikipedia.org/wiki/Secchi_disk Secchi disk].
:
* While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". The terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length, but not all of the water can actually "precipitate". An unambiguous and currently-used standard name for this quantity is: "atmosphere_water~vapor" + "z_integral_from_bottom-to-top_of_volume_fraction".
:
* See Altitude, Elevation, Height and Thickness.

 


== {{ Bar Heading| text=Diameter}} ==

  base_quantity = "diameter"

  ''Examples''
basin_channel-network_graph__diameter
graph~tree~rooted__diameter
tree~oak~bluejack_trunk__diameter
impact-crater_circle__diameter (see '''Object_name + model_name Pattern''')
square__diameter

* This quantity usually has units of length (except for rooted tree graphs).
:
* Although often associated with a circle, the general definition of [http://en.wikipedia.org/wiki/Diameter diameter] is the maximum distance (for some metric) between any two points in a set. So any bounded geometric shape (e.g. a square or any polygon) has a well-defined diameter, as does any bounded set of points. Note that the diameter of a bounded set is the same as the diameter of its [http://en.wikipedia.org/wiki/Convex_hull convex hull]. In graph theory, the diameter of a rooted [http://en.wikipedia.org/wiki/Tree_graph tree graph] is the maximum number of edges between the root and any leaf. River networks have a well-defined diameter (though topological vs. geometrical) since they can be viewed as rooted tree graphs (rooted at the outlet).
:
* See Perimeter.

 


== {{ Bar Heading| text=Diffusivity}} ==

  base_quantity = "diffusivity" 
  ''Examples of Specific Quantities:'' 
  "magnetic_diffusivity" [m2 s-1] 
  "mass_diffusivity" [m2 s-1] 
  "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity) 
  "thermal_diffusivity" [m2 s-1] 

* It appears that the units are always [m2 s-1].
:
* "thermal_diffusivity" seems preferable to "heat_diffusivity"
:
* Common adjectives are: biharmonic, laplacian, epineutral, etc.
:
* The term "eddy diffusivity" is sometimes used as a synonym for the "eddy diffusion coefficient", usually denoted as "K". See: [http://en.wikipedia.org/wiki/Eddy_diffusion Eddy diffusion].
:
* See: [http://en.wikipedia.org/wiki/Magnetic_diffusivity Magnetic diffusivity], [http://en.wikipedia.org/wiki/Mass_diffusivity Mass diffusivity], [http://en.wikipedia.org/wiki/Kinematic_viscosity#Kinematic_viscosity Kinematic viscosity], [http://en.wikipedia.org/wiki/Momentum_diffusion Momentum diffusion], [http://en.wikipedia.org/wiki/Thermal_diffusivity Thermal diffusivity] and [http://en.wikipedia.org/wiki/Heat_conduction Thermal conduction].

 


== {{ Bar Heading| text=Dimension}} ==

  base_quantity = "dimension" 
  ''Examples of Specific Quantities:'' 
  "box_counting_dimension" 
  "hausdorff_dimension" 

  ''Examples''
cantor-set__hausdorff_dimension
peano-curve__hausdorff_dimension
sierpinski-gasket__hausdorff_dimension

* This quantity is usually used in connection with fractals and it can be measured (usually using the box-counting dimension) for many objects in nature.
:
* See: [http://en.wikipedia.org/wiki/Box-counting_dimension Box-counting dimension], [http://en.wikipedia.org/wiki/Dimension Dimension], [http://en.wikipedia.org/wiki/Fractal_dimension Fractal dimension], [http://en.wikipedia.org/wiki/Hausdorff_dimension Hausdorff dimension] and [http://en.wikipedia.org/wiki/Packing_dimension Packing dimension].

 


== {{ Bar Heading| text=Dimensionless Numbers}} ==

  [ famous person's name ] + "_number"

  ''Examples''
air_helium-plume__richardson_number
airplane__mach_number
channel_water_flow__froude_number
channel_water_flow__reynolds_number
equation~heat__courant_number #### (insert "model" ??)
ship__froude_number

* Dimensionless numbers are widely used in physics and typically obtained as the ratio of two quantities that have the same units. For example, Reynolds number gives the ratio of inertial and viscous forces in a flow problem, and flows transition from laminar to turbulent as the Reynolds number increases.
:
* Wikipedia has a nice table of [http://en.wikipedia.org/wiki/Dimensionless_number '''dimensionless numbers'''] which provides numerous examples.
:
* Some names, like "Reynolds", end in "s", but a possessive "s" is not added at the end. See the CSDMS Standard Name [[CSN_Basic_Rules | '''Basic Rules''']].
:
* The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.
:
* See the Attributes of Atoms and Number templates for terms like "proton_number".
:
* See the Number template for more information.

 


== {{ Bar Heading| text=Discharge or Volume Flow Rate}} ==

  "volume_flow_rate" 
  ''Examples of Specific Quantities:'' 
  
  ''Examples''
channel_water_x-section__volume_flow_rate [m3 s-1]
lake_water~incoming__volume_flow_rate [m3 s-1]
lake_water~outgoing__volume_flow_rate [m3 s-1]

* The term "discharge" is used primarily by hydrologists and is commonly denoted as "Q". The term "volume_flow_rate" is more broadly understood.
:
* The term "discharge" has the connotation of something leaving a domain, so additional clarification is generally needed to indicate whether the volume flow rate is into or out of a given domain (e.g. with "incoming" or "outgoing"). The quantity names '''''incoming_volume_flow_rate''''' and '''''outgoing_volume_flow_rate''''' are always unambiguous.
:
* Hydrologists also use "unit_width_discharge" (discharge per unit contour width) in the context of surface flows. It is usually denoted by lower-case "q" and has SI units of [m2 s-1]. Note that "depth-integrated velocity" is a synonym for unit-width discharge, and in CSN this 2D vector field is called "z_integral_of_velocity". Note that the "lateral inflow rate" to the sides of a channel is given by: "channel_bank_water" + "volume-per-length_flow_rate".
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate], [http://en.wikipedia.org/wiki/Volumetric_flux Volumetric flux] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* A "volume_flux" has units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volume flux over the cross-sectional area of a channel or pipe. See the Flux template.
:
* Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.
:
* If a "sediment discharge" quantity has units of [mass / time], then it should be called something like "channel_water_sediment~suspended" + "mass_flow_rate" instead of "channel_water_sediment~suspended" + "volume_flow_rate", since discharge has units of [volume / time].
:
* See the '''Flow Rate''' template.

 


== {{ Bar Heading| text=Distance}} ==

  base_quantity = "distance" 
  ''Examples of Specific Quantities:'' 
  "average_distance" 
  "separation_distance"

  ''Examples''
channel_centerline_endpoints__separation_distance
earth-to-sun__average_distance

* This quantity seems to require specifying two objects, just as solubility, partial_pressure and volume_fraction do. In the latter cases the special keyword "_in_" was introduced. Here the reserved word "-to-" and the pattern: (object + "-to-" + object + distance) is used in a similar way. The keyword "-to-" can also be used for ratios. See "Ratios".
:
* We could introduce "straight_distance" as a synonym for '''euclidean_distance''' or just use the latter term. Or perhaps use "euclidean_length" instead?
:
* The word "distance" is sometimes used in a more abstract sense, as a measure of dissimilarity between two objects. For example, the [http://en.wikipedia.org/wiki/Hamming_distance Hamming distance] measures the dissimilarity of two text strings. See: [http://en.wikipedia.org/wiki/Metric_(mathematics) Metric], [http://en.wikipedia.org/wiki/Distance Distance], [http://en.wikipedia.org/wiki/Euclidean_distance Euclidean distance], [http://en.wikipedia.org/wiki/Uniform_norm Uniform norm] and [http://en.wikipedia.org/wiki/Taxicab_geometry Taxicab geometry] (or "Manhattan distance").

 


== {{ Bar Heading| text=Duration}} ==

  base_quantity = "duration" 
  ''Examples of Specific Quantities:'' 
  [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  ''Examples''
aircraft__flight_duration
atmosphere_water__precipitation_duration (vs. "rainfall duration")
earth_day~sidereal__duration
earth_day~solar-mean__duration
earth_day~stellar__duration
land_surface__sunshine_duration (or "daylight_duration")
water_scuba-diver__dive_duration

* Used to indicate a time period.
:
* See the Precipitation section.
:
* Typically preceded by a process name modifier. See [[ CSN_Process_Names | CSDMS Process Names ]] for a list of process names.

 


== {{ Bar Heading| text=Efficiency}} ==

  base_quantity = "efficiency" 
  ''Examples of Specific Quantities:'' 
  "electrical_efficiency" 
  "luminous_efficiency" 
  "mechanical_efficiency" 
  "thermal_efficiency"

  ''Examples''
engine__thermal_efficiency

* Efficiency is usually expressed as a ratio of what is achieved to the max possible (or ideal) value and is therefore a dimensionless number.
:
* See: [http://en.wikipedia.org/wiki/Carnot_heat_engine Carnot heat engine], [http://en.wikipedia.org/wiki/Electrical_efficiency Electrical efficiency], [http://en.wikipedia.org/wiki/Energy_conversion_efficiency Energy conversion efficiency], [http://en.wikipedia.org/wiki/Fuel_efficiency Fuel efficiency], [http://en.wikipedia.org/wiki/Luminous_efficacy Luminous efficiency], [http://en.wikipedia.org/wiki/Mechanical_advantage Mechanical advantage], [http://en.wikipedia.org/wiki/Mechanical_efficiency Mechanical efficiency] and [http://en.wikipedia.org/wiki/Thermal_efficiency Thermal efficiency].

 


== {{ Bar Heading| text=Elevation}} ==

  base_quantity = "elevation"

  ''Examples''
bedrock_surface__elevation
land_subsurface_sat-zone_top__elevation (vs. ground_water-table_surface) ####
land_surface__elevation
sea_water_surface__elevation

* There is a subtle but important difference between the quantities "altitude" and "elevation". The word '''altitude''' refers to the distance of an object (e.g. aircraft, air parcel or balloon) above the ground, regardless of the local elevation of the land surface. The word '''elevation''' refers to the distance of an object (typically a land surface) above a datum, such as the mean sea level datum. Elevation is one of the three Geographic coordinates used to specify a 3D location (i.e. elevation, latitude and longitude).
:
* See the quantity templates for Altitude, Depth, Height, Thickness.
:
* See the object template for Surface. Elevation is one of many attributes that can be associated with a surface.
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Emissivity}} ==

  base_quantity = "emissivity"

  ''Examples''
land_surface__emissivity

* Emissivity is a measure of the effectiveness of a surface in emitting energy as '''thermal radiation''' (also called "longwave radiation"). It is defined as the (dimensionless) ratio of the thermal radiation emitted by a surface/object and the thermal radiation that would be emitted by an ideal '''black body''' surface at the same temperature.
:
* Emissivity values are dimensionless and range between 0 and 1.
:
* See: [http://en.wikipedia.org/wiki/Black_body Black body], [http://en.wikipedia.org/wiki/Black-body_radiation Black-body radiation], [http://en.wikipedia.org/wiki/Earth's_energy_budget Earth's energy budget], [http://en.wikipedia.org/wiki/Emissivity Emissivity], [http://en.wikipedia.org/wiki/Outgoing_longwave_radiation Outgoing longwave radiation] and [http://en.wikipedia.org/wiki/Shortwave_radiation Shortwave radiation].

 


== {{ Bar Heading| text=Emittance}} ==

  base_quantity = "emittance"

  ''Examples''
land_surface_radiation~incoming~longwave__emittance

* Emittance is the '''energy flux''' emitted by a source, and has SI units of [W m-2] or [J m-2 s-1].
:
* See: [http://en.wikipedia.org/wiki/Irradiance Irradiance].
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Energy}} ==

  base_quantity = "energy" 
  ''Examples of Specific Quantities:'' 
  "electric_energy" 
  "free_energy" 
  "internal_energy" 
  "kinetic_energy" 
  "potential_energy" 
  "thermal_energy"

  ''Examples''
projectile__potential_energy
water__gibbs_free_energy

* The SI unit for energy is Joules.
:
* Specific energy is energy per unit volume or mass. Add the prefix mass-specific, mole-specific or volume-specific for clarity.
:
* Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See [http://en.wikipedia.org/wiki/Energy Energy].
:
* See [https://en.wikipedia.org/wiki/Chemical_energy Chemical energy], [https://en.wikipedia.org/wiki/Chemical_potential Chemical potential], [https://en.wikipedia.org/wiki/Elastic_energy Elastic energy], [https://en.wikipedia.org/wiki/Electrical_energy Electrical energy], [https://en.wikipedia.org/wiki/Extent_of_reaction Extent of reaction], [https://en.wikipedia.org/wiki/Fermi_energy Fermi energy], [https://en.wikipedia.org/wiki/Food_energy Food energy], [http://en.wikipedia.org/wiki/Gibbs_free_energy Gibbs free energy], [http://en.wikipedia.org/wiki/Helmholtz_free_energy Helmholtz free energy], [https://en.wikipedia.org/wiki/Internal_energy Internal energy] and [https://en.wikipedia.org/wiki/Magnetic_energy Magnetic energy], [https://en.wikipedia.org/wiki/Magnetic_moment Magnetic moment], [http://en.wikipedia.org/wiki/Thermodynamic_free_energy Thermodynamic free energy].

 


== {{ Bar Heading| text=Enthalpy}} ==

  base_quantity = "enthalpy" 
  
  ''Examples of Specific Quantities:'' 
  "atomization_enthalpy" 
  "combustion_enthalpy" 
  "denaturation_enthalpy" 
  "dissolution_enthalpy" (also called "enthalpy of solution") 
  "formation_enthalpy" 
  "fusion_enthalpy" 
  "hydration_enthalpy" 
  "hydrogenation_enthalpy" 
  "mass-specific_enthalpy" 
  "mixing_enthalpy" 
  "reaction_enthalpy" 
  "sublimation_enthalpy" 
  "vaporization_enthalpy"

  ''Examples''

* Enthalpy is defined as the "thermodynamic potential", computed as H = U + pV, where U = internal energy, p = pressure and V = volume. It has SI units of Joules.
:
* Add the prefix "mole-specific" to a quantity like "combustion_enthalpy" when the units are Joules per mole.
:
* See: [http://en.wikipedia.org/wiki/Enthalpy Enthalpy].

 


== {{ Bar Heading| text=Exponent}} ==

  base_quantity = "exponent"

  ''Examples''
basin__flint_law_exponent
basin_channel~longest__hack_law_exponent
channel_water_sediment~suspended__volume_flow_rate_law_area_exponent
glacier__glen_law_exponent

* Exponents often occur in empirical laws.
:
* Systems that can undergo [http://en.wikipedia.org/wiki/Phase_transitions phase transitions] are often characterized by a [http://en.wikipedia.org/wiki/Critical_exponents critical exponent].
:
* See Coefficient, Constant, Factor, Index, Number and Parameter.

 


== {{ Bar Heading| text=Factor}} ==

  base_quantity = "factor"

  ''Examples''
oscillator__q_factor
pipe_water_flow__darcy_friction_factor (same as moody_friction_factor)
pipe_water_flow__fanning_friction_factor
sun-lotion_skin__protection_factor (known as SPF)
wave~sine__crest_factor

* Use "manning_n_parameter" instead of "manning_friction_factor".
:
* Many different types of [http://en.wikipedia.org/wiki/Shape_factor_(image_analysis-and-microscopy) Shape factor] are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".
:
* Another type of shape factor is given by the square root of area divided by the shape's diameter (max distance between any 2 boundary points.).
:
* A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".
:
* See: [http://en.wikipedia.org/wiki/Atomic_form_factor Atomic form factor] (or atomic scattering factor), [http://en.wikipedia.org/wiki/Crest_factor Crest factor], [http://en.wikipedia.org/wiki/Cunningham_correction_factor Cunningham correction factor] (for small particles in a fluid), [http://en.wikipedia.org/wiki/Q_factor Q factor], [http://en.wikipedia.org/wiki/Sun_protection_factor#Sun_Protection_Factor Sun Protection Factor (SPF)] and [http://en.wikipedia.org/wiki/View_factor View factor].
:
* See Coefficient, Constant, Exponent, Index, Number and Parameter.

 


== {{ Bar Heading| text=Flag}} ==

  base_quantity = "flag"

  ''Examples''
model__**_option_flag

* We may want to allow "flag" as a quantity since many models provide options as boolean values known as "flags". It isn't clear yet, however, how these would be shared between models or what the object_name would be.
:
* See [http://en.wikipedia.org/wiki/Flag_(computing) Flag (computing)].


== {{ Bar Heading| text=Flow Rate}} ==

  base_quantity = "flow_rate" 
  ''Examples of Specific Quantities:'' 
  "mass_flow_rate" 
  "momentum_flow_rate" 
  "energy_flow_rate" 
  "volume_flow_rate" 
  "mole_flow_rate"

  ''Examples''
channel_entrance_water_x-section__volume_flow_rate
channel_exit_water_x-section_sediment~suspended__mass_flow_rate
lake_water~incoming__volume_flow_rate

* The quantity name "flow_rate" can be ambiguous in the context of a fluid that can either flow into or out of the object in the object part of the name. In such cases, the process names "inflow" and "outflow" can be used instead of "flow" and are viewed relative to the object. While "discharge" is commonly used as a quantity name in hydrology, it connotes a volume outflow rate and sounds strange when used to refer to a volume ''inflow''.
:
* The base quantity "rate" implies that units of inverse time are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flow_rate [ kg s-1 ]
momentum_flow_rate [ kg m s-2 ]
energy_flow_rate [ J s-1 ] = [ W ]
volume_flow_rate [ m3 s-1 ]
mole_flow_rate [ mol s-1 ]
:
* "Energy flow rate" is also known as "power". See: [http://en.wikipedia.org/wiki/Power_(physics) Power].
:
* See: [http://en.wikipedia.org/wiki/Discharge_(hydrology) Discharge], [http://en.wikipedia.org/wiki/Volumetric_flow_rate Volumetric flow rate] and [http://en.wikipedia.org/wiki/Mass_flow_rate Mass flow rate].
:
* See the templates for Discharge, Flux and Rate of a Process.



== {{ Bar Heading| text=Flux}} ==

  base_quantity = "flux" 
  ''Examples of Specific Quantities:'' 
  "mass_flux" 
  "momentum_flux" 
  "energy_flux" 
  "volume_flux" 
  "mole_flux" (perhaps this should be "number_flux" to be independent of units.) 
  process_name + "_flux"   (e.g. "radiation_flux")

  ''Examples''
land_surface_radiation~outgoing~longwave__energy_flux (emitted and upward)
land_surface_radiation~incoming~longwave__energy_flux (incident and downward)

* See the section on Radiation on the [[CSN_Quantity_Templates | CSDMS Quantity Templates]] page for many examples of radiation fluxes.
:
* In the context of "transport phenomena", the definition of "flux" is '''''flow rate per unit area'''''. In addition to the phrase "per unit area", this definition includes the word '''''rate''''' which implies per unit time. So the base quantity "flux" implies that units of [m-2 s-1] are added to the units of the quantity that is being transported. For example, in SI units we have:
mass_flux [ kg m-2 s-1 ]
momentum_flux [ kg m s-1 m-2 s-1 ] = [ kg m-1 s-2 ] = [ Pa ] (force per unit area, same units as "pressure")
energy_flux [ W m-2 ] = [ J m-2 s-1 ]
volume_flux [ m s-1] = [ m3 m-2 s-1 ]
mole_flux [ mol m-2 s-1 ]
:
* "Flux" can also be understood as "surface bombardment rate".
:
* "Flow rate" is the total amount of the transported quantity per unit time, or the product of an area and a flux. Replacing "flux" with "flow_rate" in a quantity name results in a different, but also valid quantity.
:
* The examples above show how the object name can be either a '''''surface''''' or a '''''medium'''''. Either type of object can potentially "absorb", "emit", "reflect" or "transmit" a flux.
:
* An energy flux ''emitted by'' an object is a quantity called '''''outgoing_radiation_flux''''' (positive if outgoing). An energy flux that is ''received by'' or ''incident on'' an object is a quantity called '''''incoming_radiation_flux''''' (positive if incoming). That is, the sun "radiates" energy and the earth is "irradiated" by this energy. This distinction means that "incident_radiation" serves as a synonym for "irradiation" and "emitted_radiation" as a synonym for "radiation". Some objects, like a land surface, can radiate longwave energy or be irradiated by longwave energy. In such cases, the term "outgoing_radiation_flux" establishes a sign convention that "outgoing is positive". Similarly, "incoming_radiation_flux" implies "incoming is positive". Process names often occur in pairs that indicate "incoming" or "outgoing", such as "emigration" and "immigration" or "exporting" and "importing". Note that a process name, like "radiation" represents an action that applies to the object in the object name part.
:
* The shortwave radiation incident on the land surface is typically modeled as the sum of three components, called '''''direct''''', '''''diffuse''''' and '''''backscattered'''''. Only the "direct" component (radiation from the sun, transmitted directly through the atmosphere to the surface) is dependent on topographic slope and aspect. The other two are emitted (via reflections from aerosols) isotropically by the atmosphere so they appear to be arriving from a direction that is parallel to the local surface normal. For the "direct" component, an extra adjective like "slope_corrected" may be needed. See: [http://en.wikipedia.org/wiki/Earth%27s_radiation_balance Earth's radiation balance].
:
* A process name frequently precedes the base quantity "flux" in accordance with the '''Process_name + Quantity Pattern'''. Examples include "evaporation_volume_flux", "precipitation_mass_flux".
:
* It turns out that '''''stress''''' and '''''momentum flux''''' both have the same units of Pascals (or N m-2, or kg m-1 s-2). When a fluid exerts a shear stress on a boundary, this results in a momentum flux into the boundary and this loss of momentum slows the flow.
:
* What about "luminous flux" (for visible light)? See: [http://en.wikipedia.org/wiki/Luminous_flux Luminous flux].
:
* See: [http://en.wikipedia.org/wiki/Flux Flux], [http://en.wikipedia.org/wiki/Transport_phenomena Transport phenomena].
:
* "Discharge" is a volume flow rate and not a flux. See Discharge.
:
* "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity
:
* In the [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names], "flux" may be preceded by the words: mass, momentum, energy, heat, longwave, shortwave, radiative, water, vapor, evaporation, palm, photon, mole, salt Units are [W m-2] for the "energy fluxes" such as: "heat", "longwave", "shortwave" and "radiative". In addition, "shortwave_radiation" is abbreviated to "shortwave".
:
* See the templates for Concentration, Discharge and Flow Rate.

 


== {{ Bar Heading| text=Force}} ==

  base_quantity = "force" 
  quantity = "braking_force" 
  quantity = "drag_force" 
  quantity = "impact_force" 
  quantity = "lift_force"

  ''Examples''
automobile__braking_force

* A force may be thought of as a push or a pull exerted on an object and has SI units of Newtons. Note that "weight" is also a force.
:
* See [https://en.wikipedia.org/wiki/Force Force].



== {{ Bar Heading| text=Fraction}} ==

  quantity_suffix = "fraction" 
  ''Examples of Specific Quantities:'' 
  "area_fraction" 
  "mass_fraction" 
  "mole_fraction" 
  "time_fraction" 
  "volume_fraction"

  ''Examples''
basin_land~forested__area_fraction
basin_land~grassland__area_fraction

earth_surface_land__area_fraction
earth_surface_water__area_fraction
# surface of a 3D region vs. mathematical surface

region_state_land~agricultural__area_fraction
region_state_land~arable__area_fraction
region_state_land~burned__area_fraction
region_state_land~cloud-covered__area_fraction
region_state_land~commercial__area_fraction
region_state_land~dry__area_fraction
region_state_land~farmed__area_fraction
region_state_land~flooded__area_fraction
region_state_land~flooded__max_of_depth ####
region_state_land~forested__area_fraction
region_state_land~grassland__area_fraction
region_state_land~grazing__area_fraction
region_state_land~ice-covered__area_fraction
region_state_land~irrigated__area_fraction
region_state_land~lake-covered__area_fraction
region_state_land~water-covered__area_fraction
region_state_land~parkland__area_fraction
region_state_land~private__area_fraction
region_state_land~public__area_fraction
region_state_land~residential__area_fraction
region_state_land~snow-covered__area_fraction
region_state_land~urban__area_fraction
region_state_land~vegetated__area_fraction
region_state_land~wetland_fraction

rocket_payload__mass_fraction
rocket_propellant__mass_fraction (See: [http://en.wikipedia.org/wiki/Propellant_mass_fraction Propellant mass fraction].)

sea_water_oxygen__volume_fraction

soil_air__volume_fraction (Object-in-Object Pattern)
soil_clay__volume_fraction
soil_ice__volume_fraction
soil_loam__volume_fraction
soil_sand__volume_fraction
soil_silt__volume_fraction
soil_water__volume_fraction (instead of "soil" + "water_content") #####

* The word "fraction" can be viewed as a "quantity suffix" (as defined at the top) that can be applied to any base quantity (e.g. area, mass, mole, time, volume) to create a new quantity. In most (if not all) cases it is dimensionless.
:
* In order for "area_fraction" and "volume_fraction" to be well-defined, the object part of the name should ideally refer to a 2D or 3D shape (e.g. polygon or polytope) for which the area or volume can be computed. (e.g. for 2D, a state or a drainage basin)
:
* If an "area fraction" variable name is used with gridded data, then the "area_fraction" applies to the area of the grid cell. If the area fraction applies to some specific domain or object, such as a U.S. state or a drainage basin, then constructions like: "basin_land~forested + area_fraction" can be used and conform to the '''Part of Another Object Pattern'''.
:
* The quantity '''''area_fraction''''' is often used in connection with the fraction of land (in map or plan view) that meets some criteria. Adjectives like "burned", "forested", "public" and "urban" can be used to define the criteria as shown in the examples. As of 7/23/14, hyphenated adjectives like "snow-covered" are allowed.
:
* If an "area fraction" variable name is meant to distinguish between two possible states, such as land and water, then a reserved word like "vs" (or "to") could be used in a construction like: "land-vs-water + area_fraction".
:
* Variable names with "volume fraction" usually use the '''Object-in-object Quantity Pattern''' as in the examples.
:
* In the CF Standard Names, "fraction" is used in 306 names to form the following 5 quantities where the number of occurrences is indicated in parentheses:
area_fraction (19)
mass_fraction (179)
mole_fraction (95)
time_fraction (2)
volume_fraction (11)

: The ones for "volume_fraction" fall into 5 groups:
ocean_volume_fraction
volume_fraction_of_oxygen_in_sea_water
volume_fraction_of_[clay, silt or sand]_in_soil
volume_fraction_of_condensed_water_in_soil + [assumptions]
volume_fraction_of_frozen_water_in_soil

: Hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil". However, using "soil_water~condensed + volume_fraction" instead is consistent with the '''Object-in-object Quantity Pattern'''.

 


== {{ Bar Heading| text=Frequency}} ==

  base_quantity = "frequency" [1/second] (but the meaning is "cycles per second") 

  ''Examples of Specific Quantities:'' 
  "angular_frequency" [radians/second] 
  "nyquist_frequency" [1/second]

  ''Examples''
cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency (also called "buoyancy_frequency")
sea_surface_water_wave__frequency

* Units of frequency are usually hertz = [1/second].
:
* Note that the word "frequency" alone means '''''temporal frequency''''' and "wavenumber" means '''''spatial frequency'''''. Note that "angular_frequency" is distinct from "frequency" and "angular_wavenumber" is distinct from "wavenumber", but they are closely related quantities.
:
* For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.
:
* See [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Brunt–Väisälä_frequency Brunt–Väisälä frequency], [http://en.wikipedia.org/wiki/Frequency Frequency], [http://en.wikipedia.org/wiki/Normalized_frequency_(digital_signal_processing) Normalized frequency] and [http://en.wikipedia.org/wiki/Nyquist_frequency Nyquist frequency].

 


== {{ Bar Heading| text=Friction}} ==
:
* Friction is not a quantity and is really a '''force''' as opposed to a process. It is not included in this list of [[CSN_Process_Names | CSDMS Process Names]] because it doesn't fit the general verb-to-noun process name pattern explained on that page. The word "traction" has similar issues.
:
* The adjective "frictional" is used in terms like "frictional_momentum_loss_rate". But the net loss of momentum (per unit time and per unit area) due to friction in a fluid is equivalent to the '''shear stress'''. Note that both have units [M L T-2]. See the template for Stress.
:
* Some quantities associated with friction are:
kinetic_friction_coefficient (See the Coefficient template.)
log_law_roughness_length ("z0" for law of the wall)
manning_n_parameter

shear_stress (See the Stress template.)
static_friction_coefficient
:
* A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

 


== {{ Bar Heading| text=Fuel Efficiency}} ==

  ''Examples of Specific Quantities:'' 
  "fuel_consumption_rate" ["gallons per mile" or "liters per km"] 
  "fuel_economy" ["miles per gallon" or "km per liter"] 
  "fuel_specific_energy_content" [Joules / kg] 

  ''Examples''
automobile_fuel__consumption_rate
automobile_fuel__economy
automobile_fuel__specific_energy_content (or energy-per-mass_content ??) #####

* In everyday language, the term "miles_per_gallon" is often used as if it were a quantity name but it is really a units name. "mileage" has various meanings and is not a well-defined quantity name.
:
* Is there a good "process - rate" quantity name for "fuel_economy" ? We could potentially replace "economy" with "per_gallon_miles".
:
* energy_efficiency and energy_intensity are related quantities.
:
* Efficiency of electric vehicles is often given as "cents_per_mile" which allows comparison to gas-powered vehicles.
:
* See: [http://en.wikipedia.org/wiki/Fuel_efficiency#Fuel_efficiency_of_vehicles Fuel efficiency of vehicles] and [http://en.wikipedia.org/wiki/Efficient_energy_use Efficient energy use].

 

== {{ Bar Heading| text=Hardness}} ==

  base_quantity = "hardness" 
  ''Examples of Specific Quantities:'' 
  "indentation_hardness" 
  "rebound_hardness" 
  "scratch_hardness"

  ''Examples''
snowpack_surface__indentation_hardness

* Hardness is a function of many things and there are 3 main types of hardness measurements called indentation hardness, rebound hardness and scratch hardness.
:
* See [http://en.wikipedia.org/wiki/Hardness Hardness] and [http://en.wikipedia.org/wiki/Scratch_hardness Scratch hardness].
:
* The word hardness is also used in chemistry, in the context of "hard water". See: [http://en.wikipedia.org/wiki/Carbonate_hardness Carbonate hardness] and [http://en.wikipedia.org/wiki/Hard_water Hard water]. ''Permanent hardness'' is defined as Calcium hardness + Magnesium hardness, while ''temporary hardness'' is a synonym for Carbonate hardness. Water hardness can be measured as a '''molar concentration''' of calcium and magnesium ions, but several alternate units are used around the world and there are conversion factors between them.

 


== {{ Bar Heading| text=Head}} ==

  base_quantity = "head" 
  ''Examples of Specific Quantities:'' 
  "friction_head" 
  "hydraulic_head" 
  "pressure_head" 
  "velocity_head"

  ''Examples''
pump__hydraulic_head
soil_water__pressure_head

* Head is a quantity used in fluid dynamics (hydraulics) that relates the energy in an incompressible fluid to the an equivalent height in a column of fluid. It has units of length.
:
* "Total hydraulic head" is the sum of the elevation head and pressure head.
:
* The "hydraulic_gradient" is computed by taking differences or derivatives of head values and determines the direction of fluid flow.
:
* See: [http://en.wikipedia.org/wiki/Hydraulic_head Hydraulic head], [http://en.wikipedia.org/wiki/Pressure_head Pressure head] and [http://en.wikipedia.org/wiki/Total_dynamic_head Total hydraulic head].

 

== {{ Bar Heading| text=Heat}} ==

  base_quantity = "heat" 
  ''Examples of Specific Quantities:'' 
  "mass-specific_fusion_latent_heat" 
  "sensible_heat"

  ''Examples''
water__mass-specific_latent_fusion_heat (334 [kJ kg-1])
water__mass-specific_latent_sublimation_heat
water__mass-specific_latent_vaporization_heat (2500 [kJ kg-1])

* The quantity "heat" refers to "thermal energy" that is being transferred from one system to another by thermal interaction. It has SI units of Joules.
:
* The word "specific" is often inserted as in "specific_latent_heat" and "specific_sensible_heat" to indicate thermal energy per unit mass [J kg-1].
:
* While the "latent heat of fusion" and "latent heat of vaporization" are constants for a given substance (e.g. water), they don't use the Constant template but are treated as in the two examples above in accordance with the '''Process_name + Quantity Pattern'''. Note that "latent_heat" is a quantity name and "fusion" and "vaporization" are process names.
:
* The quantities "advection_heat_flux", "conduction_heat_flux", "latent_heat_flux" and "sensible_heat_flux" are also used.
:
* See: [http://en.wikipedia.org/wiki/Heat Heat], [http://en.wikipedia.org/wiki/Latent_heat Latent heat], [http://en.wikipedia.org/wiki/Sensible_heat Sensible heat] and [http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances Thermodynamic databases for pure substances].
:
* See Energy and Flux of Heat or Energy.

 


== {{ Bar Heading| text=Height}} ==

  base_quantity = "height" 
  ''Examples of Specific Quantities:'' 
  "geopotential_height" 
  "reference_height"

  ''Examples''
building~empire-state__height
human__mean_height
tree~oak~bluejack__mean_height

* See [http://en.wikipedia.org/wiki/Geopotential_height Geopotential height], [http://en.wikipedia.org/wiki/Geostrophic_wind Geostrophic wind] and [http://en.wikipedia.org/wiki/Above_mean_sea_level Above mean sea level].
:
* See Reference Quantities.

 


== {{ Bar Heading| text=Humidity and Relative Saturation}} ==

  base_quantity = "humidity" 
  ''Examples of Specific Quantities:'' 
  "absolute_humidity" (is "volumetric_humidity" a synonym ?) 
  "relative_humidity" 
  "relative_saturation" 
  "specific_humidity" 

  ''Examples''
atmosphere_air_carbon-dioxide__relative_saturation ## CHECK
atmosphere_air_water~vapor__relative_saturation (instead of air_relative_humidity)

* Relative humidity is a dimensionless ratio of partial pressures. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture (often called the "vapor pressure") to the saturated vapor (partial) pressure of the water at a prescribed temperature.
:
* The relative humidity is often known (measured) and empirical equations for computing saturated vapor pressure as a function of temperature have been given by both Brutsaert and Satterlund. From these, vapor pressure can be computed from the definition.
:
* Relative humidity of air depends on both temperature and pressure.
:
* The more general term for relative humidity (when not talking about water vapor in air) is '''relative_saturation'''. It is the ratio of the partial pressure to the saturated partial pressure of one (condensable phase) gas in another (non-condensable phase) gas mixture.

 

== {{ Bar Heading| text=Impedance}} ==

  base_quantity = "impedance" 
  ''Examples of Specific Quantities:'' 
  "acoustic_impedance" 
  "characteristic_acoustic_impedance" 
  "characteristic_electrical_impedance" 
  "electrical_impedance" 
  "mechanical_impedance" 
  "nominal_electrical_impedance" 
  "specific_acoustic_impedance" 
  "wave_impedance" 

  ''Examples''
None yet

* Electrical impedance is a complex-valued quantity, where the real part is the familiar [http://en.wikipedia.org/wiki/Electrical_resistance '''resistance'''] (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance'''].
:
* [http://en.wikipedia.org/wiki/Admittance '''Admittance'''] is defined as the inverse of impedance, and is therefore also complex-valued. Its real part is called '''conductance''' (with SI unit "siemens") and its complex part is called: [http://en.wikipedia.org/wiki/Susceptance '''susceptance'''].
:
* See: [http://en.wikipedia.org/wiki/Acoustic_impedance Acoustic impedance], [http://en.wikipedia.org/wiki/Electrical_impedance Electrical impedance], [http://en.wikipedia.org/wiki/Impedance_(Accelerator_Physics) Impedance (Accelerator Physics)], [http://en.wikipedia.org/wiki/Mechanical_impedance Mechanical impedance] and [http://en.wikipedia.org/wiki/Wave_impedance Wave impedance].
:
* Also see: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance] and [http://en.wikipedia.org/wiki/Inductance Inductance].

 


== {{ Bar Heading| text=Impulse}} ==

  base_quantity = "impulse" 
  ''Examples of Specific Quantities:'' 
  "impact_impulse"

  ''Examples''
baseball-bat_baseball__impact_impulse

* An "impulse" quantifies the change in linear momentum that results from a force applied over a time interval. It has units of (force x time), and SI units of [N s].
:
* See: [http://en.wikipedia.org/wiki/Impulse_(physics) Impulse (physics)].

 


== {{ Bar Heading| text=Increment}} ==

  operation_prefix = "increment_of"

  ''Examples''
atmosphere_air__increment_of_pressure
bedrock_surface__increment_of_elevation
land_surface__increment_of_elevation

* This can be used for the change in a quantity that occurs over some time period, such as a model time step. Models often update state variables with each time step by an incremental amount and this amount may be the quantity of interest. Note that an increment can be positive or negative.
:
* Before 3/19/13 this was treated as a '''quantity suffix''' but now it is treated as an "operation prefix". See Anomaly, Component, Limit, Magnitude, Ratio and Scale.
:
* For an "increment_of_time", the quantity suffix "step" is usually used instead of "increment". See the Step and Time Step templates.

 


== {{ Bar Heading| text=Index}} ==

  base_quantity = "index"

  ''Examples''
atmosphere_air_radiation__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
land_surface__topographic_wetness_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index ################
__palmer_drought_index

* The word "index" serves as a '''''base quantity''''' in the CSDMS Standard Names. It has two distinct meanings. One meaning of index is a subscript to an array, as used in "model_grid_cell__column_index" and "model_grid_cell__row_index" above. In this case, the index is a nonnegative integer. A second, and widely-used meaning for index is a '''composite statistic''' or '''measure'''. See the Wikipedia article: [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)]. Examples of this type include: Consumer Price Index, Normalized Difference Vegetation Index, Palmer Drought Index, Topographic Wetness Index and Urban Accessibility Index and others listed below.
:
* Perhaps we should use the word ''subscript'' instead of index for the first meaning of index above.
:
* In order to distinguish between many different indices of a certain type, such as a [http://en.wikipedia.org/wiki/Diversity_index ''diversity index''], the last name of the author who introduced a particular index (and also the publication year, if necessary) can be used as a prefix to disambiguate, as in ''shannon_diversity_index''.
:
* We use "refraction_index" instead of "refractive_index" in accordance with the '''Process_name + Quantity Pattern'''. See Attributes of Radiation for information on the "standard_refraction_index".
:
* See Coefficient, Constant, Exponent, Factor, Number and Parameter.
:
* See: [http://en.wikipedia.org/wiki/Diversity_index Diversity index], [http://en.wikipedia.org/wiki/Forest_fire_weather_index Forest fire weather index], [http://en.wikipedia.org/wiki/Haines_Index Haines index], [http://en.wikipedia.org/wiki/Heat_index Heat index], [http://en.wikipedia.org/wiki/Index_(economics) Index (economics)], [http://en.wikipedia.org/wiki/Index_(statistics) Index (statistics)], [http://en.wikipedia.org/wiki/Jaccard_index Jaccard index], [http://en.wikipedia.org/wiki/Lifted_index Lifted index], [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index Normalized Difference Vegetation Index], [http://en.wikipedia.org/wiki/Palmer_Drought_Index Palmer drought index], [http://en.wikipedia.org/wiki/Price_index Price index], [http://en.wikipedia.org/wiki/Producer_price_index Producer Price Index], [http://en.wikipedia.org/wiki/Refraction_index Refraction index] and [http://en.wikipedia.org/wiki/S%26P_Dow_Jones_Indices S & P Dow Jones Indices], [http://en.wikipedia.org/wiki/Stock_market_index Stock market index], [http://en.wikipedia.org/wiki/Topographic_Wetness_Index Topographic Wetness Index].

 


== {{ Bar Heading| text=Inertia}} ==

  base_quantity = "inertia" 
  ''Examples of Specific Quantities:'' 
  "rotational_inertia" [kg m2] 
  "thermal_inertia" [J m-2 K-1 s-0.5] 
  "translational_inertia" [kg] (sometimes used as a synonym for "mass")

  ''Examples''
projectile__rotational_inertia
sea_water__thermal_inertia

* The term '''inertia''' by itself refers to the degree to which an object resists changes to its translational motion, which depends only on its mass. The term "translational inertia" (a synonym for mass?) is sometimes used for clarity, especially since the concept of inertia lends its name to the quantity names "rotational inertia" (also called moment of inertia) and "thermal inertia".
:
* The concept of inertia comes from Newton's first law of motion and can be stated as: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted on by an external force." It is often summarized with the adage: "Objects in motion tend to stay in motion. Objects at rest tend to stay at rest."
:
* '''Rotational inertia''' is also called "moment of inertia" and is a measure of the resistance to an object to changes in its angular momentum.
:
* The '''thermal inertia''' of a material is a measure of its resistance to changes in temperature. It is defined as the square root of the product of thermal conductivity, mass density and mass specific thermal capacity.
:
* Thermal inertia is an "intensive property" since it involves mass specific thermal capacity.
:
* See [http://en.wikipedia.org/wiki/Inertia Inertia], [http://en.wikipedia.org/wiki/Moment_of_inertia Moment of inertia] (rotational inertia), [http://en.wikipedia.org/wiki/Thermal_effusivity Thermal effusivity] and [http://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia Thermal inertia].

 


== {{ Bar Heading| text=Intensity}} ==

  base_quantity = "intensity" 
  ''Examples of Specific Quantities:'' 
  "luminous_intensity" (optics) 
  "radiant_intensity" (optics) 
  "sound_intensity" (or "acoustic_intensity") 

  ''Examples''
atmosphere_air_radiation~incoming~shortwave__energy_intensity [ W m-2] ############# energy_flux ??

* Intensity is an overloaded term, but often means "power per unit area" and is therefore equivalent to an "energy flux".
:
* It is not yet clear when (or if) the CSDMS Standard Names should use "intensity" instead of "energy_flux", which is more descriptive. See Flux.
:
* See: [http://en.wikipedia.org/wiki/Intensity_(physics) Intensity (physics)], [http://en.wikipedia.org/wiki/Radiant_intensity Radiant intensity] and [http://en.wikipedia.org/wiki/Sound_intensity Sound intensity].

 


== {{ Bar Heading| text=Latitude}} ==

  base_quantity = "latitude" 
  ''Examples of Specific Quantities:'' 
  "authalic_latitude" 
  "conformal_latitude" 
  "geocentric_latitude" 
  "geodetic_latitude" 
  "isometric_latitude" 
  "rectifying_latitude" 
  "reduced_latitude"

  ''Examples''
model_grid_cell_center__geodetic_latitude
model_grid_cell_edge~north__geodetic_latitude
model_grid_cell_edge~south__geodetic_latitude
model_grid_edge~north__geodetic_latitude
model_grid_edge~south__geodetic_latitude

* For an ellipsoid (of the type used to model the shapes of planets), there are many different ways to define latitude, but really just one way to define longitude. This is because the longitude lines (meridians) trace out ellipses (of the same size and shape) while the latitude lines are circles (of different sizes). When unqualified, the word "latitude" usually refers to '''geodetic latitude'''. The other six types of latitude are called "auxiliary latitudes" and are used for special problems in geodesy. Full explanations of these different types of latitude are provided at the links below.
:
* For a spheroid, the various definitions of latitude become the same. This is because the equatorial and polar radius are then the same, so the flattening, f, and eccentricity, e, are both zero. This can be checked by inserting e=0 into formulas for [http://en.wikipedia.org/wiki/Latitude#Auxiliary_latitudes '''auxiliary latitudes'''].
:
* Typical units for latitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Longitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Limit}} ==

  operation_prefix = "limit_of" 

  ''Examples''
human__lower_limit_of_hearing_frequency (Note: hearing is a process name)
human__upper_limit_of_hearing_frequency
human_eye_photon__lower_limit_of_detection_number (process_name + quantity)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass

* Before 3/19/13 this was treated as a '''quantity suffix''', but now it is treated as an "operation prefix". See Anomaly, Component, Increment and Magnitude. A "limit" is not a quantity by itself, but is an operation that can be applied to virtually any quantity.
:
* For clarity, it is often necessary to insert an adjective like "lower" or "upper" before the word "limit", as in the examples above.
:
* Note that the two limits above named after people include the quantity name "limit_mass" instead of "limit_of_mass". There is also a related "Schwarzchild radius"; see the quantity template for Radius. It is not clear that "_limit" would ever be used by itself. See Point.
:
* "cutoff" or "threshold" may sometimes be used similarly.

 


== {{ Bar Heading| text=Longitude}} ==

  base_quantity = "longitude"

  ''Examples''
model_grid_cell_center__longitude
model_grid_cell_edge~east__longitude
model_grid_cell_edge~west__longitude
model_grid_edge~east__longitude
model_grid_edge~west__longitude

* While there are several different ways to define '''latitude''' for an ellipsoid, there is really just one way to define longitude, as explained in the Latitude section.
:
* Since "center", "edge~east", "edge~west", etc. refer to parts of a cell, it is consistent with the use of similar words like "bottom" and "top" to include these in the object name part of the name (as of 7/23/14). Hyphens are used as shown here to clarify that "edge~east" is a single object or sub-object.
:
* Typical units are "decimal degrees".
:
* Typical units for longitude are "decimal degrees".
:
* This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Coupling Metadata (MCM) file. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".
:
* Note: Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?
:
* See the sections for Coordinates and Latitude.
:
* See: [http://en.wikipedia.org/wiki/Colatitude Colatitude], [http://en.wikipedia.org/wiki/Geodetic_datum Geodetic datum], [http://en.wikipedia.org/wiki/Geographic_coordinate_system Geographic coordinate system], [http://en.wikipedia.org/wiki/Geographical_distance Geographical distance], [http://en.wikipedia.org/wiki/Latitude Latitude], [http://en.wikipedia.org/wiki/Longitude Longitude], [http://en.wikipedia.org/wiki/Meridian_arc Meridian arc] and [http://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid].

 


== {{ Bar Heading| text=Magnitude}} ==

  "magnitude_of_" + [vector quantity]

  ''Examples''
sea_bottom_water__magnitude_of_shear_stress
sea_water__magnitude_of_vorticity

* Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.
:
* The quantity name "speed" should be used instead of "magnitude_of_velocity".
:
* This was changed from a "quantity suffix" to a vector operation on 2/7/13. See [[CSN_Operation_Templates | CSDMS Operation Templates]].
:
* In the CF Standard Names, "magnitude_of_" is a transformation (used as a prefix to an entire name) that is used in about 5 names.

 


== {{ Bar Heading| text=Mask}} ==

  base_quantity = "mask"

  ''Examples''
land_mask
ocean_mask

* In computer graphics and geographic information systems (GIS), the word "mask" is used to indicate a gridded (usually 2D or 3D) binary mask where two values (e.g. 0 and 1) are used to indicate whether or not a given feature or property is present in that grid cell. The term "data mask" is sometimes used to indicate that grid cells contain a data value if they are in the mask and a nodata value otherwise.
:
* A mask is often associated with a threshold value of some other grid of data. For example, a "land mask" may be set to 1 for every grid cell with an elevation value greater than 0 and set to 0 otherwise. We could use a standard name like "elevation_threshold_mask" or "temperature_threshold_mask" and then define the threshold value and how the masked values are related to the threshold value (>, >=, <, <= or =) with an <assume> tag in a Model Coupling Metadata (MCM) file.
:
* Masks provide a mechanism to identify a subset of a larger set, so they are a way to refer to a part of a larger object. Because of this, it is reasonable to use "land-mask" as an object in the object part of a CSDMS Standard Name. However, it is also reasonable to use "binary_mask" as a quantity name since it indicates the possible values (0 and 1) and the absence of units. A "data mask", on the other hand, inherits the quantity name and units of the data. So it would be reasonable to use "data_mask_of" as an operation, as in "positive_data_mask_of_elevation".
:
* The [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] currently have two names that contain the word "mask", namely: "land_binary_mask" and "sunlit_binary_mask". The guidelines mention both "binary_mask" and "data_mask".
:
* Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the '''Process_name + Quantity Pattern'''.
:
* Note that painters use [http://en.wikipedia.org/wiki/Masking_tape Masking tape] to "mask off" areas that should not be painted.
:
* See: [http://en.wikipedia.org/wiki/Binary_image Binary image] and [http://en.wikipedia.org/wiki/Mask_(computing) Mask (computing)].

 


== {{ Bar Heading| text=Mass}} ==

  base_quantity = "mass" 
  ''Examples of Specific Quantities:'' 
  "molar_mass" 
  "relativistic_mass" 
  "rest_mass"

  ''Examples''
### cesium_atomic_mass (also relative_atomic_mass = atomic_weight)
electron__relativistic_mass
electron__rest_mass (also invariant mass, intrinsic_mass, proper mass)
star~neutron__tolman_oppenheimer_volkoff_limit_mass
star~white-dwarf__chandrasekhar_limit_mass (object = star~white-dwarf)

* The SI units for mass are kilograms.
:
* What about "biomass"?
:
* See Attributes of Atoms, Concentration, Flux.
:
* See: [http://en.wikipedia.org/wiki/Added_mass Added mass], [http://en.wikipedia.org/wiki/Biomass Biomass], [http://en.wikipedia.org/wiki/Invariant_mass Invariant mass], [http://en.wikipedia.org/wiki/Mass-energy_equivalence Mass-energy equivalence], [http://en.wikipedia.org/wiki/Mass_in_special_relativity Mass in special relativity], [http://en.wikipedia.org/wiki/Molar_mass Molar mass], [http://en.wikipedia.org/wiki/Planck_mass Planck mass] and [http://en.wikipedia.org/wiki/Transverse_mass Transverse mass].

 


== {{ Bar Heading| text=Maximum}} ==

  ''Examples''
basin_outlet_water_x-section__time_max_of_volume_flow_rate (for "peak discharge')

* While we could use "max" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Miles per Gallon}} ==

* This is not allowed because it is not a good quantity name; it is really a units name. The associated concepts are "fuel_consumption" and "fuel_economy". The word "mileage" is sometimes used but is also a poor term.
:
* See the Fuel Efficiency template.

 

== {{ Bar Heading| text=Minimum}} ==

  ''Examples''
basin_outlet_water_x-section__time_min_of_volume_flow_rate

* While we could use "min" as a quantity suffix, this is not unambiguous for quantities that can vary in both space and time, such as drainage basin discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: [[CSN_Operation_Templates | '''CSDMS Operation Templates''']].

 


== {{ Bar Heading| text=Modulus}} ==

  base_quantity = "modulus" 
  ''Examples of Specific Quantities:'' 
  "bulk_modulus" 
  "shear_modulus" 
  "young_modulus"

  ''Examples''
lithosphere__bulk_modulus
lithosphere__young_modulus

* This quantity is used in continuum mechanics and materials science to measure a material's resistance to different types of deformation, sometimes called rigidity or stiffness. It has units of pressure.
:
* Bulk, shear and Young's are different types of "elastic modulus".
:
* There are several different models for how the shear modulus of metals varies with pressure and/or temperature, such as the MTS, SCG and NP models. See: [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus].
:
* See: [http://en.wikipedia.org/wiki/Bulk_modulus Bulk modulus], [http://en.wikipedia.org/wiki/Dynamic_modulus Dynamic modulus], [http://en.wikipedia.org/wiki/Elastic_modulus Elastic modulus], [http://en.wikipedia.org/wiki/Lamé_parameters Lamé parameters], [http://en.wikipedia.org/wiki/P-wave_modulus P-wave modulus], [http://en.wikipedia.org/wiki/Poisson%27s_ratio Poisson's ratio], [http://en.wikipedia.org/wiki/Shear_modulus Shear modulus] and [http://en.wikipedia.org/wiki/Young%27s_modulus Young's modulus].

 


== {{ Bar Heading| text=Number}} ==

  base_quantity = "number" 
  ''Examples of Specific Quantities:'' 
  "julian_day_number" 
  "neutron_number" 
  "proton_number" 
  "quantum_number" 
  "wavenumber" 
  "winding_number"

  ''Examples''
automobile__vehicle_identification_number (i.e. VIN number)
carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_surface_water_wave__wavenumber

* This quantity name is often used when the attribute being quantified can only take integer values, as in the examples above and detectors that count particles. The word "count" is used similarly.
:
* Many important '''dimensionless numbers''' also end with the word "number" and are often named after a person (e.g. Reynolds number). These are discussed in the Dimensionless Number template and they are typically not integers. Also the [http://en.wikipedia.org/wiki/Wave_number wave number] need not be an integer.
:
* Sometimes, there are multiple definitions for a dimensionless number, so they aren't always interchangeable. For example, there are at least 4 types of [http://en.wikipedia.org/wiki/Richardson_number Richardson number]. One is the reciprocal of the square of the Froude number. Three others are used in atmospheric science and are preceded by the adjective "flux", "gradient" or "bulk" (an approximation to the gradient version). For some definitions, the Richardson number can only take positive values, while for others it can also take negative values, which indicates an unstable atmosphere. The AMS provides several definitions of the [http://glossary.ametsoc.org/wiki/Richardson_number Richardson number].
:
* Atomic number is a synonym for "proton_number" but the latter is used for clarity and consistency in the CSDMS standard names. The "mass_number" is defined as the sum of the "proton_number" and "neutron_number".
:
* Atomic physics uses several [http://en.wikipedia.org/wiki/Quantum_number quantum_numbers], including the: [http://en.wikipedia.org/wiki/Principal_quantum_number principal quantum number], [http://en.wikipedia.org/wiki/Azimuthal_quantum_number azimuthal quantum number], [http://en.wikipedia.org/wiki/Magnetic_quantum_number magnetic quantum number], [http://en.wikipedia.org/wiki/Spin_quantum_number spin quantum number] and [http://en.wikipedia.org/wiki/Topological_quantum_number topological quantum number].
:
* Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".
:
* The [http://en.wikipedia.org/wiki/Winding_number winding number] is used in mathematics as an attribute of closed, planar curves.
:
* See: [http://en.wikipedia.org/wiki/Atomic_number Atomic number], [http://en.wikipedia.org/wiki/Lepton_number Lepton number] and [http://en.wikipedia.org/wiki/Neutron_number Neutron number].
:
* Unique identification numbers are often assigned to people and other objects. See [http://en.wikipedia.org/wiki/Credit_card_number Credit card number],[http://en.wikipedia.org/wiki/Employer_Identification_Number Employer Identification Number] (EIN), [http://en.wikipedia.org/wiki/Enzyme_Commission_number Enzyme Commission Number], [http://en.wikipedia.org/wiki/National_identification_number National Identification Number], [http://en.wikipedia.org/wiki/Numbering_scheme Numbering scheme], [http://en.wikipedia.org/wiki/Social_Security_Number Social Security Number], [http://en.wikipedia.org/wiki/TC_number Transporter Classification Number] and [http://en.wikipedia.org/wiki/Vehicle_Identification_Number Vehicle Identification Number] (VIN).
:
* In the branch of mathematics called ''number theory'' there are many special numbers, often named after a famous person. The [http://en.wikipedia.org/wiki/On-Line_Encyclopedia_of_Integer_Sequences Online Encyclopedia of Integer Sequences] (OEIS) maintains an extensive database of information on integer sequences. See: [http://en.wikipedia.org/wiki/Bell_number Bell number], [http://en.wikipedia.org/wiki/Catalan_number Catalan number], [http://en.wikipedia.org/wiki/Euler_number Euler number], [http://en.wikipedia.org/wiki/Fibonacci_number Fibonacci number], [http://en.wikipedia.org/wiki/1729_(number) Hardy-Ramanujan number], [http://en.wikipedia.org/wiki/Kaprekar_number Kaprekar number], [http://en.wikipedia.org/wiki/Lucas_number Lucas number], [http://en.wikipedia.org/wiki/Prime_number Prime number] and [http://en.wikipedia.org/wiki/Smith_number Smith number]. Also see the template for Constants in Math.
:
* For hydrologic features such as rivers, unique identification numbers such as the [http://en.wikipedia.org/wiki/United_States_Geological_Survey USGS] [http://en.wikipedia.org/wiki/Hydrological_code Hydrologic Unit Code] (or "HUC number") and Pfafstetter Code are used. See Code.
:
* See the Count template and [http://en.wikipedia.org/wiki/Julian_day Julian day].

 


== {{ Bar Heading| text=Parameter}} ==

  base_quantity = "parameter"

  ''Examples''
channel_bottom_water_flow_sediment__shields_parameter
channel_water_flow__manning_n_parameter
soil_water__van_genuchten_alpha_parameter

* Parameters often occur in empirical laws.
:
* The CSDMS Standard Names use "manning_n_parameter vs. "manning_coefficient".
:
* The CSDMS standard names use "coriolis_frequency" vs. "coriolis_parameter".
:
* Shields (1935) worked with a nondimensional shear stress that is now known as the Shields parameter.
:
* See templates for Coefficient, Constant, Exponent, Factor, Index and Number.

 


== {{ Bar Heading| text=Partial Pressure}} ==

  base_quantity = "partial_pressure" 
  ''Examples of Specific Quantities:'' 
  name = [substance 1] + "_" + [substance 2] + "_partial_pressure"

  ''Examples''
atmosphere_carbon-dioxide__partial_pressure # (carbon dioxide in air)
atmosphere_water~vapor__partial_pressure # (water vapor in air)
atmosphere_water~vapor__saturated_partial_pressure

* This is an example of a quantity that uses the '''Object-in-object Quantity Pattern''' because two substances are involved. See Solubility and Volume Fraction.
:
* The term "water vapor pressure" refers to the partial pressure of water vapor in air, and the "saturated water vapor pressure" is the partial pressure of water vapor in air at saturation. The CSDMS standard names for these are given above. One of them uses the '''Saturated Quantity Rule'''.
:
* Partial pressure for a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in '''''equilibrium''''' with the liquid at the same temperature. See: [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure].
:
* CF Standard Names currently has only 6 names with "partial_pressure". They all have units of [Pa] and are:

surface_carbon_dioxide_partial_pressure_difference_between_air_and_sea_water
surface_carbon_dioxide_partial_pressure_difference_between_sea_water_and_air
surface_molecular_oxygen_partial_pressure_difference_between_sea_water_and_air
surface_partial_pressure_of_carbon_dioxide_in_air
surface_partial_pressure_of_carbon_dioxide_in_sea_water
water_vapor_partial_pressure_in_air (alias: water_vapor_pressure)

:We could use the following CSDMS standard name for the first quantity listed above:
"sea_surface_air-vs-water_carbon-dioxide" + "difference_of_partial_pressure"
(with "difference" as a quantity suffix). Or with a new rule for "-and-in_", we could use:
surface_carbon_dioxide_in_air-and-in_sea_water_partial_pressure_difference.

* See the quantity template for Pressure.

 


== {{ Bar Heading| text=Perimeter}} ==

  base_quantity = "perimeter"

  ''Examples''
basin_boundary__perimeter
channel_x-section__perimeter

* This quantity has units of length and is well-defined for virtually any (nonfractal) planar shape. It can be infinite, however, for a fractal shape such as the [http://en.wikipedia.org/wiki/Koch_snowflake Koch snowflake].
:
* See Diameter.

 


== {{ Bar Heading| text=Period}} ==

  base_quantity = "period" 
  ''Examples of Specific Quantities:'' 
  "sidereal_period" 
  "synodic_period"

  ''Examples''
earth__rotation_period
flood__expected_return_period ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_surface_water_wave__period
virus_chicken-pox__incubation_period

* This quantity has units of time and is typically used to describe the time required for some time of ''periodic'' motion to return to its starting point. Examples include the rotation of a planet on its axis, the orbit of a planet around the sun or the period of a wave.
:
* In hydrology the terms: [http://en.wikipedia.org/wiki/Return_period Return period], "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.
:
* See: [http://en.wikipedia.org/wiki/Orbital_period Orbital period] for definitions of "sidereal period", "synodic period", "draconic period", "anomalistic period" and "tropical period".
:
* The '''Process_name + Quantity Pattern''' is often used, as in: "digestion period", "dormant period", [http://en.wikipedia.org/wiki/Gestation_period gestation period], [http://en.wikipedia.org/wiki/Hibernation Hibernation period], [http://en.wikipedia.org/wiki/Incubation_period incubation period], [http://en.wikipedia.org/wiki/Rotation_period rotation period], "sleeping period"], [http://en.wikipedia.org/wiki/Waiting_period waiting period] and [http://en.wikipedia.org/wiki/Wave_period wave period].
:
* See Duration and Time.

 


== {{ Bar Heading| text=Permeability}} ==

  base_quantity = "permeability"

  ''Examples''
sea_bottom_sediment__permeability

* Permeability is a property of a geologic material (and not the fluid) that indicates the ability of a fluid to move through it. It is related to '''hydraulic conductivity'''.
:
* See [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity] and [http://en.wikipedia.org/wiki/Permeability_(earth_sciences) Permeability] (earth sciences).

 


== {{ Bar Heading| text=pH}} ==

  base_quantity = "ph"

  ''Examples''
channel_water__ph
sulfuric-acid_solution__ph

* This quantity measures the [http://en.wikipedia.org/wiki/Activity_(chemistry) activity] of the (solvated) hydrogen ion in a solution. It is close to 7 for pure water, less than 7 for acidic solutions and greater than 7 for basic (i.e. alkaline) solutions.
:
* Should "pH" be viewed as a measurement unit instead of a quantity?
:
* See: [http://en.wikipedia.org/wiki/PH Wikipedia: pH].

 


== {{ Bar Heading| text=Point}} ==

  ''Examples''
boiling_point
breaking_point ??
bubble_point
critical_point (See: [http://en.wikipedia.org/wiki/Critical_temperature Critical point].)
curie_point (See: [http://en.wikipedia.org/wiki/Curie_point Curie point].)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point (used in infiltration theory)
yield_point (See: [http://en.wikipedia.org/wiki/Yield_strength Yield strength].)

atmosphere_water~vapor__dew_point_temperature
atmosphere_water~vapor__frost_point_temperature
ice__melting_point_temperature
water__boiling_point_temperature
water__freezing_point_temperature

* This is not viewed as a quantity or quantity suffix within the CSDMS Standard Names. It is generally inserted just before a base quantity name and refers to a '''threshold''' that occurs for that quantity. See the template for Temperature for many examples.
:
* Each of the examples above puts a "process name" prefix, from the list of process names in [[CSN_Process_Names | '''CSDMS Process Names''' ]] in front of "_point".

 


== {{ Bar Heading| text=Porosity}} ==

  base_quantity = "porosity"

  ''Examples''
soil__porosity

* Could also be called "soil_air__volume_fraction".

 

== {{ Bar Heading| text=Power}} ==

  base_quantity = "power"

  ''Examples''
channel_water__power

* "Power" has SI units of [J s-1] = [ W ]. In the context of a fluid in motion, it is an "energy flow rate" associated with the kinetic energy of the fluid. It is proportional to the cube of the fluid velocity. For a non-accelerating flow, the gravitational acceleration of the flow is exactly balanced by the loss of momentum due to friction. See the template for Flow Rate.
:
* In hydrology, the terms "stream_power" and "unit_width_stream_power" are used. See: [http://en.wikipedia.org/wiki/Stream_power Stream power].

 

== {{ Bar Heading| text=Precipitation}} ==

  "precipitation_" + base_quantity 
  "precipitation_leq-volume_flux 
  "precipitation_mass_flux 
  "precipitation_volume_flux

  ''Examples''
atmosphere_water__precipitation_duration
atmosphere_water__precipitation_leq-volume_flux (in liquid or solid form)
atmosphere_ice__precipitation_volume_flux
atmosphere_snow__precipitation_volume_flux
titan_atmosphere_methane__precipitation_leq-volume_flux (on Titan)

* Precipitation is not a quantity, but rather a process as defined at the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_volume_flux" has units of [length / time] (e.g. mm per hour) and a "precipitation_mass_flux" has units of [mass / time] (e.g. kg per hour).
:
* "Rainfall" is a somewhat unusual example of a process name in that the relevant object (rain) and the associated process (falling) have been fused to create the process name. Adding the object part in front would mean repeating the word rain. But "rain" is also a verb and "raining" is therefore a valid process name, but only for liquid water. The CSDMS Standard Names avoid this issue by using the process name "precipitation" instead of "rainfall" or "raining" and then specifying the object that is precipitating, such as "water" or perhaps "methane" for Titan.
:
* Since water can precipitate in liquid or solid form, each with a different density, precipitation rates are often quantified as '''liquid-water equivalent'''. The corresponding CSDMS standard name is: "atmosphere_water" + "precipitation_leq-volume_flux", where "leq-volume" is an abbreviation for "liquid-equivalent volume". This quantity name generalizes to other substances (like methane on Titan). See: Precipitation (chemistry) and Precipitation (meteorology).
:
* Note that in the CSDMS Standard Names, it is considered unnecessary and redundant to insert "liquid_equivalent" into the names "ice" + "melt_volume_flux" and "snowpack" + "melt_volume_flux", since the process of melting converts ice and snow to liquid water.
:
* The name "snowpack" + "liquid_equivalent_depth" is also used and is computed by multiplying the snowpack depth by the "liquid-water-to-snow_density_ratio".
:
* The word "water" by itself does not indicate whether the state is gas, liquid or solid.
:
* See the templates for Process Attributes and Rates of Processes for more information.

 


== {{ Bar Heading| text=Pressure}} ==

  base_quantity = "pressure" 
  ''Examples of Specific Quantities:'' 
  "dynamic_pressure" 
  "osmotic_pressure" 
  "radiation_pressure" 
  "partial_pressure" (See Partial Pressure above) 
  "stagnation_pressure" 
  "static_pressure" 
  "total_pressure" 
  "vapor_pressure"

  ''Examples''
atmosphere_bottom_air__pressure
channel_bottom_water__static_pressure
channel_bottom_water_flow__dynamic_pressure
channel_bottom_water_flow__total_pressure
channel_water__static_pressure
channel_water_flow__dynamic_pressure (anywhere in the channel)
channel_water_flow__total_pressure

* Pressure may be thought of as "force per unit area".
:
* There is a distinction between [http://en.wikipedia.org/wiki/Static_pressure '''static pressure'''] and [http://en.wikipedia.org/wiki/Dynamic_pressure '''dynamic pressure''']. The first results from the weight of fluid above a location (called "hydrostatic" when the fluid is water) while the second is the kinetic energy per unit volume of a fluid flow. The "total pressure" is the sum of these two contributions. Also see: [http://en.wikipedia.org/wiki/Bernoulli%27s_principle Bernoulli's principle], [http://en.wikipedia.org/wiki/Pressure Pressure] and [http://en.wikipedia.org/wiki/Stagnation_Pressure Stagnation pressure].
:
* Pressure requires specifying a single object (e.g. air) but "partial pressure" requires two different objects to be specified using the "object-in-object" pattern. See the quantity template for Partial Pressure.
:
* In chemistry, the term [http://en.wikipedia.org/wiki/Vapor_pressure '''vapor pressure'''] (also called "equilibrium vapor pressure") has a specific meaning, and is a property of a single compound or substance.
:
* In meteorology, the term "vapor pressure" is used to mean the [http://en.wikipedia.org/wiki/Partial_pressure '''partial pressure'''] of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. In the CSDMS Standard Names, the term "vapor pressure" is only used as it is defined in chemistry, and for meteorology, names use "partial_pressure" or "saturated_partial_pressure" as in: "atmosphere_air_water~vapor" + "partial_pressure".
:
* Electromagnetic radiation exerts [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure'''] on an illuminated surface. A [http://en.wikipedia.org/wiki/Crookes_radiometer Crookes radiometer] is often used to illustrate this effect, but it is now known that a combination of Einstein and Reynolds forces (thermal transpiration) is actually responsible for making them turn.
:
* The quantity [http://en.wikipedia.org/wiki/Pressure_head '''pressure head'''] is used in hydraulics and in ground water modeling but it has units of length. It is often negative, and negative pressure is sometimes called ''suction''. See Head.
:
* In geology, the term [http://en.wikipedia.org/wiki/Overburden_pressure '''overburden pressure'''] or ''confining_pressure'', is used.
:
* Although the pressure generated by a sound wave is sometimes called [http://en.wikipedia.org/wiki/Sound_pressure '''sound pressure'''], the standard name would then be something like: "air_sound-wave" + "pressure".
:
* In cosmology, there is also a concept of "negative pressure".
:
* Note that "atmosphere_bottom_air" + "pressure" and "land_surface_air" + "pressure" would mean the same thing, but the former is preferred.
:
* See: [http://en.wikipedia.org/wiki/Atmospheric_pressure Atmospheric pressure], [http://en.wikipedia.org/wiki/Dynamic_pressure Dynamic pressure], [http://en.wikipedia.org/wiki/Osmotic_pressure Osmotic pressure], [http://en.wikipedia.org/wiki/Overburden_pressure Overburden pressure], [http://en.wikipedia.org/wiki/Partial_pressure Partial pressure], [http://en.wikipedia.org/wiki/Pressure Pressure], [http://en.wikipedia.org/wiki/Pressure_head Pressure head], [http://en.wikipedia.org/wiki/Radiation_pressure Radiation pressure], [http://en.wikipedia.org/wiki/Stagnation_pressure Stagnation pressure], [http://en.wikipedia.org/wiki/Static_pressure Static pressure], [http://en.wikipedia.org/wiki/Surface_tension Surface tension] and [http://en.wikipedia.org/wiki/Vapor_pressure Vapor Pressure].

 


== {{ Bar Heading| text=Process Attributes}} ==

  [ process name ] + [ base_quantity ]

  ''Examples''
digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
lapse_rate,
-------------------------------------------------------------------
evaporation_mass_flux, infiltration_mass_flux, melt_mass_flux,
precipitation_mass_flux

evaporation_volume_flux, infiltration_volume_flux, melt_volume_flux,
precipitation_volume_flux
-------------------------------------------------------------------
conception_date
delivery_date (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date (or "start_date" ??)
----------------------
precipitation_duration
sunshine_duration
----------------------
failure_frequency
oscillation_frequency
vibration_frequency
wave_frequency (vs. "waving")
----------------------
recovery_time
starting_time
stopping_time
----------------------
flow_speed
running_speed
wind_speed (Note: "wind" = "air_flow".)
----------------------
birth_weight
dissociation_energy
penetration_depth
striking_distance
turning_radius

* Many quantity names are created by pairing a process name with a base quantity name. See the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page for a long list of examples.
:
* Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See [[ CSN_Process_Names | '''CSDMS Process Names''' ]] for details and a long list of examples.
:
* Pairing a process name with the base quantity name "rate" makes sense for most processes, but a given process if often naturally associated with other base quantities (e.g. gestation_period). See the Rate template for examples where the base quantity is "rate".
:
* In the example of "birth_weight", "birth" is a process that is happening to the baby, while "delivery" or "giving birth" is the process happening to the mother. (i.e. "infant_birth_weight" and perhaps "pregnant_female_delivery_date")

 


== {{ Bar Heading| text=Radiation}} ==

  "radiation_" + quantity

  ''Examples''
light-bulb~incandescent__radiant_intensity ? ##### CHECK
universe__cosmic_background_radiation_frequency

* See the [[CSN_Examples | '''CSDMS Standard Names Examples''']] page for many examples where "radiation" is viewed as an object and appears in the object part of the name and the quantity is an energy_flux. These examples include the atmosphere, glacier, land_surface, sea_water and snowpack. Together they cover most of the Earth's basic radiation budget.
:
* Note that "radiation" (the process where an object generates and sends out energy) and "irradiation" (the process where an object receives energy from a source) are really distinct processes, and neither is a quantity by itself. The object in the object part of the name is either radiating energy or being irradiated by some external source of energy. However, as of 7/23/14, the adjectives "incoming" and "outgoing" are used instead of distinguishing between these two process names. (Similarly, "inflow" and "outflow" will not be used for fluid flow quantities.) This provides additional flexibility with semantic matching and provides a single, general and more easily understood rule. Quantity names can be constructed using the '''''Process_name + Quantity Pattern'''''. See the Process Attributes template.
:
* Incoming fluxes generated externally (from the point of view of the object name) and outgoing fluxes generated internally both have positive signs, by convention.
:
* The adjectives "upwelling" and "downwelling" are frequently used to mean "from the ground" and "from the sky". Note that "upwelling" longwave radiation would include longwave radiation emitted by the land surface as well as longwave radiation reflected from the land surface, but originally emitted from clouds or aerosols. So far, these adjectives are not used in the CSDMS Standard Names.
:
* Adjectives like longwave, shortwave, microwave, visible, infrared, thermal-infrared, ultraviolet and so on are typically inserted just before the word radiation.
:
* In a vacuum (e.g. space), the refraction index for all wavelengths of light is 1, so the speed of light is independent of wavelength. In other media, such as air and water, the refraction index (and therefore the speed) varies with wavelength. See the Index template.
:
* Radiation fluxes are '''energy fluxes''' (see the Flux template) and have SI units of [W m-2] = [J m-2 s-1].

 


== {{ Bar Heading| text=Radius}} ==

  base_quantity = "radius"

  ''Examples''
automobile__turning_radius
black-hole__schwarzchild_radius
earth_ellipsoid__equatorial_radius
earth_ellipsoid__polar_radius
railway_curve__minimum_radius (see link below)

* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Bend_radius Bend radius], [http://en.wikipedia.org/wiki/Bohr_radius Bohr radius], [http://en.wikipedia.org/wiki/Classical_electron_radius Classical electron radius], [http://en.wikipedia.org/wiki/Covalent_radius Covalent radius], [http://en.wikipedia.org/wiki/Earth_radius Earth radius] (which gives several possible definitions), [http://en.wikipedia.org/wiki/Filling_radius Filling radius], [http://en.wikipedia.org/wiki/Ionic_radius Ionic radius], [http://en.wikipedia.org/wiki/Minimum_railway_curve_radius Minimum Railway Curve Radius], [http://en.wikipedia.org/wiki/Radius_of_curvature_(mathematics) Radius of curvature (mathematics)], [http://en.wikipedia.org/wiki/Schwarzschild_radius Schwarzschild Radius], [http://en.wikipedia.org/wiki/Turning_radius Turning Radius], [http://en.wikipedia.org/wiki/Van_der_Waals_radius Van der Waals radius] and [http://en.wikipedia.org/wiki/Wigner-Seitz_radius Wigner-Seitz radius].
:
* What about Radius of Curvature? See the object template for Surface.

 


== {{ Bar Heading| text=Rate}} ==

  base_quantity ="rate" 
  ''Examples of Specific Quantities:'' 
  [ process name ] + "_rate"

  ''Examples''
atmosphere_air__temperature_lapse_rate
automobile_fuel__consumption_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate

* The word "rate" means '''per unit time''' and is often paired with a process name to create a quantity name that quantifies how fast the process occurs, as in the examples above.
:
* Quantity names like: "evaporation rate", "infiltration rate", "melt rate" and "precipitation rate" are ambiguous because these rates can be quantified with either a mass flux [kg m-2 s-1] or a volume flux [m s-1]. (The latter is what is usually meant.) So, for example, we can have "glacier_ice" + "melt_mass_flux", "glacier_ice" + "melt_volume_flux", "evaporation_mass_flux", "evaporation_volume_flux", etc.
:
* Many examples of process names (and a definition) are given on the [[CSN_Process_Names | '''CSDMS Process Names''']] page.
:
* Many examples of the Process Name + Base Quantity Name Pattern are given on the [[CSN_Process_Quantity_Names | '''CSDMS Process Name + Quantity Name Pattern''']] page.
:
* When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Coupling Metadata (MCM) file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CSDMS Standard Names, "leq-volume" is used as an abbreviation for "liquid-equivalent volume". In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.
:
* Terms like "rainfall_rate" and "rain_rate", though commonly used, do not lend themselves to our general (object + quantity) pattern. Note that "rainfall" is a contraction of object (rain) and process (falling) names.
:
* See Precipitation.

 


== {{ Bar Heading| text=Ratio}} ==

  base_quantity = "ratio" 
  ''Examples of Specific Quantities:'' 
  "aspect_ratio" 
  "bowen_ratio" 
  "dilution_ratio" 
  "mass_ratio"

  ''Examples''
bear_brain-to-body__mass_ratio
earth_ellipsoid__inverse_of_flattening_ratio
engine_air-to-fuel__mass_ratio (or "mixture_ratio")
fuel-to-oxidizer__equivalence_ratio ###
image__aspect_ratio
lake__bowen_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio

channel_x-section__width-to-depth_ratio
electron__charge-to-mass_ratio

* Some ratios are the ratio of the same quantity as measured for two different objects while others are ratios of two different quantities measured on a single object. The '''Object-to-object Quantity Pattern''' is used for the first case and the '''Quantity-to-Quantity Pattern''' is used for the second case. Examples for both cases are given above.
:
* Ratios are often dimensionless. In fact, most dimensionless numbers are ratios of forces, etc. See the Dimensionless Number template.
:
* "ratio" serves as a quantity suffix in quantities like "mass_ratio", but is also allowed as a base quantity.
:
* Note that "relative_roughness" is a quantity that is defined as the ratio of the roughness length scale and the water depth in a channel. So ''channel_bed_relative_roughness'' is a valid standard name but ''channel_bed_roughness_length-to-water_depth_ratio'' is also valid.
:
* "aspect_ratio" generally means the ratio of the lengths of the long and short sides of a rectangle; 1 for a square and > 1 otherwise.
:
* In chemistry, "dilution_ratio" and "dilution_factor" are used for a solute in a solvent.
:
* In meteorology and hydrology, the [http://en.wikipedia.org/wiki/Bowen_ratio Bowen ratio] is defined to be the ratio of sensible and latent heating of a water body.
:
* In geodesy, the "flattening ratio" and "inverse flattening ratio" are used to characterize a standard ellipsoid. See [http://en.wikipedia.org/wiki/Flattening Flattening].
:
* There are many ratios in economics, including "debt-to-credit_ratio", [http://en.wikipedia.org/wiki/Debt_ratio Debt ratio], [http://en.wikipedia.org/wiki/Debt-to-GDP_ratio Debt-to-GDP ratio], [http://en.wikipedia.org/wiki/Debt-to-income_ratio Debt-to-income ratio] and [http://en.wikipedia.org/wiki/Loan-to-value_ratio Loan-to-value_ratio].
:
* See [http://en.wikipedia.org/wiki/Fineness_ratio Fineness ratio], [http://en.wikipedia.org/wiki/Mass_ratio Mass ratio], [http://en.wikipedia.org/wiki/Poisson_ratio Poisson ratio], [http://en.wikipedia.org/wiki/Power-to-weight_ratio Power-to-weight ratio] and [http://en.wikipedia.org/wiki/Ratio Ratio].

 


== {{ Bar Heading| text=Reference Quantities}} ==

  "reference_" + quantity1 + "_" + quantity2 
  quantity1 + "_reference_" + quantity2

  ''Examples''
atmosphere_air_radiation__standard_refraction_index

land_surface_wind__reference_height_speed
land_surface_wind__speed_reference_height ("reference" is between the quantities)

sea_surface_air__reference_pressure ?? (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??

soil__reference_depth_temperature
soil__temperature_reference_depth

* Many quantities are defined with respect to a reference value of some quantity such as: height, pressure, temperature or wavelength. For example, wind speed is often reported for a reference height of 10 meters. Similarly, a model may require soil temperature at a reference depth of 1 meter.
:
* The "standard refraction index" for a given medium (e.g. air, water, vacuum) is given for a reference wavelength of 589 nm. For the latter, an <assume> tag should be included in the Model Metadata File that specifies: "at_reference_wavelength_of_589_nm" (and maybe also "yellow_doublet_sodium_d_line_reference".)
:
* Note that this typically requires that '''two''' quantities be specified, e.g "reference_height" and "speed", that result in a matched pair of distinct quantity names. These two names follow the "quantity" patterns given above.
:
* These quantities typically contain a word like "reference" or "standard". These two words may be treated as reserved words in the CSDMS Standard Names.
:
* Many quantities are defined for "standard_temperature-and-pressure" or STP and this is one of the standardized [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] that can be specified with an <assume> tag. However, there is not one standard definition of STP. The IUPAC (International Union of Pure and Applied Chemistry) defines STP as air at a temperature of 0 degrees C and a pressure of 10^5 Pa. In the US and elsewhere, STP is defined as air at a temperature of 60 degrees F and 14.696 psia (1 atm). An additional <assume> tag will therefore be required to avoid ambiguity.
:
* Many quantities, such as [http://en.wikipedia.org/wiki/Geopotential_height geopotential height] are defined relative to Earth's [http://en.wikipedia.org/wiki/Mean_sea_level mean sea level] or MSL. An <assume> tag is needed to define the corresponding reference value.
:
* Georeferenced quantities, such as elevation, require specifying a [http://en.wikipedia.org/wiki/Reference_ellipsoid reference ellipsoid]. There is typically an associated datum and a projection may also be specified. Standard names for ellipsoids, datums and projections are provided on the [[CSN_Metadata_Names | '''CSDMS Metadata Names''']] page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.
:
* In [http://en.wikipedia.org/wiki/Cumulative_frequency_analysis cumulative frequency analysis] (e.g. flood frequencies), a reference value must be specified and this would also be done using an <assume> tag.
:
* One or more <assume> tags should be used in the Model Metadata File to define the reference quantity. For example, <assume> reference_height_is_10m </assume>. The value of the reference height ("10m" in this example) should not be given in the standard name itself.
:
* The quantity suffix "Anomaly" also requires providing <assume> tags in a Model Metadata File to specify how the "mean climatology" reference value is defined.

 


== {{ Bar Heading| text=Reflectance}} ==

  base_quantity = "reflectance" 
  ''Examples of Specific Quantities:'' 
  "broadband_reflectance" 
  "spectral_reflectance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__reflectance

* Reflectance (also called "reflectivity") is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''reflected''''' by a surface to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 (for a perfectly black surface) and 1 (for a perfectly white surface).
:
* Absorptance + Reflectance + Transmittance = 1. See Reflectance and Transmittance below.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* '''Reflectance''' is the square of the magnitude of the "reflection coefficient" from [http://en.wikipedia.org/wiki/Fresnel_equations '''Fresnel's equation''']. In general, the refraction index and reflection coefficient are complex numbers, as they are for materials that can absorb radiation.
:
* The quantity "spectral reflectance" is the reflectance associated with a specific wavelength, while "broadband reflectance" is an integral over a range of wavelengths. If a radiation band like "shortwave" or "longwave" is specified in the object part of the name, then it is unnecessary to specify broadband or spectral in the quantity part.
:
* Albedo is a very closely related concept. See Albedo above.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Albedo Albedo], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Fresnel_equations Fresnel equations], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Resistance}} ==

  base_quantity = "resistance" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistance" 
  "stomatal_resistance" 
  "specific_thermal_resistance" 
  "thermal_resistance"

  ''Examples''
None yet.

* Electrical impedance is a complex-valued quantity, where the real part is the familiar '''resistance''' (with SI unit "ohm") and the imaginary part is the less-familiar [http://en.wikipedia.org/wiki/Electrical_reactance '''reactance''']. See Impedance above.
:
* '''Conductance''' is the inverse of resistance, with SI unit "siemens".
:
* There is also: [http://en.wikipedia.org/wiki/Antibiotic_resistance Antibiotic resistance].
:
* See: [http://en.wikipedia.org/wiki/Capacitance Capacitance], [http://en.wikipedia.org/wiki/Electrical_reactance Electrical reactance], [http://en.wikipedia.org/wiki/Electrical_resistance Electrical resistance], [http://en.wikipedia.org/wiki/Inductance Inductance] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Resistivity}} ==

  base_quantity = "resistivity" 
  ''Examples of Specific Quantities:'' 
  "electrical_resistivity" [siemens-1 m] or [ohm m] 
  "hydraulic_resistivity" [m-1 s] 
  "ionic_resistivity" 
  "thermal_resistivity" [W-1 m K] (this is an intensive property; don't need to add "specific") 

  ''Examples''
snow__thermal_resistivity

* '''Resistivity''' is the reciprocal of '''conductivity''' and both are "intensive" properties, so the prefix "specific" is not needed.
:
* '''Resistance''' and '''conductance''' are also reciprocals, but are "extensive" properties.
:
* See: [http://en.wikipedia.org/wiki/Electrical_resistivity-and-conductivity, [http://en.wikipedia.org/wiki/Hydraulic_conductivity Hydraulic conductivity], [http://en.wikipedia.org/wiki/Ionic_conductivity Ionic conductivity], [http://en.wikipedia.org/wiki/Thermal_conductivity Thermal conductivity] and [http://en.wikipedia.org/wiki/Thermal_resistance Thermal resistance].

 


== {{ Bar Heading| text=Scale}} ==

  quantity_suffix = "scale" 
  ''Examples of Specific Quantities:'' 
  "length_scale" 
  "time_scale" 
  "velocity_scale"

  ''Examples''
*_batchelor_scale
*_kolmogorov_length_scale
*_kolmogorov_time_scale
*_kolmogorov_velocity_scale
*_mesoscopic_length_scale
*_obukhov_length_scale
*_planck_length_scale
*_planck_time_scale
*_taylor_length_scale

* This is another quantity suffix, used to create new quantity names from existing quantity names. It often is used to indicate the value of a quantity that is as small as it can be for the given system and therefore able to serve as a natural unit of measure.
:
* The adjective "characteristic" is often inserted before the base quantity name, as in "characteristic_length_scale".
:
* See: [http://en.wikipedia.org/wiki/Length_scale Length scale], [http://en.wikipedia.org/wiki/Kolmogorov_microscales Kolmogorov microscales], [http://en.wikipedia.org/wiki/Batchelor_scale Batchelor scale] and [http://en.wikipedia.org/wiki/Taylor_microscale Taylor microscale].
:
* See [http://en.wikipedia.org/wiki/Natural_units Natural units], [http://en.wikipedia.org/wiki/Planck_units Planck units], [http://en.wikipedia.org/wiki/Planck_length Planck length] and [http://en.wikipedia.org/wiki/Planck_time Planck time].
:
* Other interesting length scales include the [http://en.wikipedia.org/wiki/Obukhov_Length Obukhov length],[http://en.wikipedia.org/wiki/Mesoscopic_scale Mesoscopic scale], [http://en.wikipedia.org/wiki/Synoptic_scale_meteorology Synoptic scale] and [http://en.wikipedia.org/wiki/Nanoscale Nanoscale].

 

== {{ Bar Heading| text=Sinuosity}} ==

  base_quantity = "sinuosity" 
  ''Examples of Specific Quantities:'' 
  "downvalley_sinuosity"

  ''Examples''
channel_centerline__downvalley_sinuosity
channel_centerline__sinuosity
channel_valley_centerline__sinuosity

* Sinuosity is a dimensionless measure of the extent to which a river channel wiggles or deviates from a more direct path. Although it can be defined in different ways, the result is always a number that is greater than or equal to 1.
:
* In geomorphology, the standard type of sinuosity — which we here call "downvalley_sinuosity" — is the ratio of the centerline length of a channel to the centerline length of the valley that contains that channel. However, the centerline length of a valley can be difficult to measure with Geographic Information System (GIS) software. The word "sinuosity" (without qualification) is the ratio of the centerline length of a channel to the straight-line distance between the two endpoints of the channel (i.e. "as the crow flies"). Note that "sinuosity" will always be greater than or equal to "downvalley sinuosity".
:
* Note that the word "centerline" is inserted in accordance with the '''Object_name + model_name Pattern''' (i.e. a model of the object in question for which "length" is well-defined) and seems preferable to "axis", "backbone" and "curve".
:
* Recall that a "geodesic" is the shortest path between two points in a space that may be curved. On the surface of a sphere, a geodesic is given by the "great circle" that passes through two given points on the sphere. In a plane, the geodesic is just the straight line segment or "chord" that connects the two points. Geometry in the plane is also called [http://en.wikipedia.org/wiki/Euclidean_geometry Euclidean geometry].
:
* Other types of sinuosity have also been defined in the literature, including: floodplain sinuosity, terrace sinuosity and meander belt sinuosity.
:
* Even in a channel with straight banks, one can define a "thalweg" sinuosity by using thalweg centerline length in the numerator.
:
* We could construct longer and more descriptive standard names for different types of sinuosities such as: <br\> "channel_centerline-to-valley_centerline" + "length_ratio" and <br\> "channel_centerline-to-straight_line" + "length_ratio". This may help to avoid ambiguity for the less common types of sinuosity. We could even replace "length_ratio" in these names with "sinuosity".
:
* The standard definitions of sinuosity and tortuosity appear to be identical. The term "sinuosity_index" is sometimes used, here called "downvalley_sinuosity". See: [http://en.wikipedia.org/wiki/Sinuosity Sinuosity] and [http://en.wikipedia.org/wiki/Tortuosity Tortuosity].
:
* See: [http://en.wikipedia.org/wiki/Chord_(geometry) Chord], [http://en.wikipedia.org/wiki/Geodesic Geodesic] and [http://en.wikipedia.org/wiki/Meander Meander].

 


== {{ Bar Heading| text=Slope}} ==

  base_quantity = "slope"

  ''Examples''
land_surface__slope

* Slope is a dimensionless measure of the local steepness of a surface. It is defined as the magnitude of the gradient of elevation. In 1D, it is computed as"rise over run".
:
* The term "slope_angle" is used for the angle, beta, such that: slope = tan( beta ), or beta = arctan( slope ).
:
* See: [http://en.wikipedia.org/wiki/Aspect_(geography) Aspect] and [http://en.wikipedia.org/wiki/Slope Slope].

 


== {{ Bar Heading| text=Solubility}} ==

  base_quantity = "solubility"

  ''Examples''
water_carbon-dioxide__solubility
water_diethyl-ether__solubility
water_ethanol__solubility

* This quantity always involves two substances and therefore requires using the '''Object-in-object Quantity Pattern'''. However, use of the reserved word "in" is now deprecated. (7/23/14). Instead, the containing object is listed first, followed by those contained and multi-word object names are hyphenated. See the templates for Partial Pressure and Fraction (volume fraction) which are similar in this regard.
:
* The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas in the solvent. See: [http://en.wikipedia.org/wiki/Solubility Solubility].
:
* [http://en.wikipedia.org/wiki/Miscibility Miscibility] is the property of liquids to mix in all proportions to form a homogeneous solution and is a closely related concept. It is not a quantity, however.

 


== {{ Bar Heading| text=Span}} ==

  base_quantity = "span"

  ''Examples''
airplane_wing__span
beam__span
bridge__span
human_life__span #### (or human_life__max_of_duration ??)

* Span is an unusual quantity name that may have units of length or time depending on the context.
:
* "Wingspan" is a contraction of an object name (part of another object) and a quantity name. An underscore is inserted in a CSDMS standard name to indicate that "span" is the base quantity.
:
* See: [http://en.wikipedia.org/wiki/List_of_spans List of spans],[http://en.wikipedia.org/wiki/Maximum_life_span Maximum life span], [http://en.wikipedia.org/wiki/Span_(architecture) Span (in architecture)], [http://en.wikipedia.org/wiki/Span_(length) Span (as a unit)] and [http://en.wikipedia.org/wiki/Wingspan Wingspan].

 

== {{ Bar Heading| text=Speed}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "escape_speed" 
  "relative_speed" 
  "settling_speed" 
  "terminal_speed"

  ''Examples''
glacier_bottom__sliding_speed
land_surface_air_flow__speed

* The quantity name "speed" is equivalent to "magnitude_of_velocity". Velocity components use the "component_of" operation prefix. See the Component template.
:
* When applied to fluids, the word "flow" is added to the end of the object part of the name, as an abbreviation for "flow field". It was formerly inserted before the word "speed".
:
* "Velocity" is a vector quantity while "speed" is a scalar quantity. The CSDMS Standard Names may allow vector quantities so that models can attempt to retrieve all velocity components in one data structure.
:
* The quantity '''relative_speed''' is the speed of one object relative to another (which may also be moving, in an arbitrary direction). In general, the "relative speed" can be computed as the magnitude of the [http://en.wikipedia.org/wiki/Euclidean_vector#Addition-and-subtraction '''vector difference'''] between the the velocity vectors of the two objects. Both objects must be named in the object part of the name as in: "aircraft_ground" + "relative_speed".
:
* See Velocity for "escape speed", "settling speed" and "terminal speed".

 


== {{ Bar Heading| text=Step}} ==

  quantity_suffix = "step"

  ''Examples''
model__time_step

* This is another '''quantity suffix''' (defined at the top) that is usually used when the base quantity is "time".
:
* While an increment can have either sign, a step is generally positive.
:
* See Increment and Time Step.

 


== {{ Bar Heading| text=Strain}} ==

  base_quantity = "strain"

* Strain is a normalized measure of deformation in continuum mechanics and is therefore dimensionless.
:
* Different fluids and substances have different "stress-strain" relationships. For a [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], there is a linear relationship between the shear stress and the strain rate.
:
* See [http://en.wikipedia.org/wiki/Deformation_(mechanics) Deformation], [http://en.wikipedia.org/wiki/Shear_stress Shear stress], [http://en.wikipedia.org/wiki/Strain_rate Strain rate] and [http://en.wikipedia.org/wiki/Stress-strain_curve Stress-strain curve].

 

== {{ Bar Heading| text=Strength}} ==

  base_quantity = "strength"

  ''Examples''
None yet.

* In physics, the "strength" of a vector field is simply its '''magnitude'''. See: [http://en.wikipedia.org/wiki/Field_strength Field strength] and [http://en.wikipedia.org/wiki/Signal_strength Signal strength]. See Magnitude above.
:
* In materials science, the word "strength" often refers to a critical value of '''stress'''. See: [http://en.wikipedia.org/wiki/Compressive_strength Compressive strength], [http://en.wikipedia.org/wiki/Shear_strength Shear strength], [http://en.wikipedia.org/wiki/Tensile_strength Tensile strength] and [http://en.wikipedia.org/wiki/Yield_strength Yield strength].
:
* See: [http://en.wikipedia.org/wiki/Physical_strength Physical strength].

 


== {{ Bar Heading| text=Stress}} ==

  base_quantity = "stress" 
  ''Examples of Specific Quantities:'' 
  "deviatoric_stress" 
  "normal_stress" 
  "shear_stress" (vs. "shearing_stress"; see below)

  ''Examples''
channel_bottom_water_flow__magnitude_of_shear_stress
channel_bottom_water_flow_sediment_grain__shields_critical_shear_stress
sea_bottom_surface_water_flow__normal_component_of_stress
sea_bottom_surface_water_flow__x_z_component_of_shear_stress
sea_water_flow__down_east_component_of_stress
sea_water_flow__down_east_component_of_reynolds_stress
sea_water_flow__down_east_component_of_viscous_stress
sea_water_flow__down_north_component_of_stress

* Components of stress are specified using the "component_of" operation prefix, as shown in the examples above. For models that use a geographic coordinate system, we would use "east", "north" and "up" to describe component directions. For models that use a Cartesian (or equal-area) coordinate system, we would use "x", "y" and "z".
:
* Standard adjectives for shear stress include: "skin_friction", "form_drag" and "total".
:
* Conventions like "right_hand_rule" and "positive_downward" can be indicated in a Model Metadata File with <assume> tags.
:
* Perhaps we should introduce a convention where "shear_stress" is taken to mean "magnitude_of_shear_stress" when there is no operation prefix.
:
* Stresses are more complex than vectors and are represented mathematically as tensors.
:
* There are two "kinds" of stress called "normal" and "shear" stress. While a normal stress is associated with a single vector, two vectors are required to describe a shear stress.
:
* Note that "shearing_stress" follows the '''Process_name + Quantity Pattern''', where the process name is "shearing". However, the "ing" ending is often dropped, as is often the case with process names; see the top of the [[CSN_Process_Names | '''CSDMS Process Names''']] page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.
:
* [http://en.wikipedia.org/wiki/Reynolds_stress Reynolds stress] is a contribution to the total stress tensor in a fluid due to momentum fluctuations that arise within turbulent flows. When "stress" appears by itself, it indicates the "total" stress tensor, which includes the so-called "viscous_stress" and the "Reynolds_stress" (or turbulent stress). (Is radiation stress also included in "total"? See below.)
:
* Shields (1935) introduced the concept of a "critical shear stress" that must be exceeded at the bed of a river channel in order to initiate sediment transport. The associated quantity name is "shields_critical_shear_stress", with the name "shields" being placed before "critical" to allow other definitions of "critical_shear_stress" by future researchers. We could use the Process Name + Base Quantity Name Pattern to construct a self-describing quantity name like: "transport_initiation_stress", "initial-transport_stress" or "initial-motion_stress".
:
* In oceanography there is a concept of '''radiation stress''' and for electromagnetic radiation there is [http://en.wikipedia.org/wiki/Radiation_pressure '''radiation pressure''']. See Pressure.
:
* There are 19 [http://cfconventions.org/Data/cf-standard-names/27/build/cf-standard-name-table.html CF Standard Names] that contain the word "stress". Most contain only one "component adjective" like "eastward", but some have two, such as

surface_downward_eastward_stress
surface_downward_northward_stress
surface_downward_x_stress
surface_downward_y_stress

 


== {{ Bar Heading| text=Temperature}} ==

  base_quantity = "temperature" 
  ''Examples of Specific Quantities:'' 
  "convective_temperature" 
  "effective_temperature" 
  "equivalent_temperature" 
  "equivalent_potential_temperature" 
  "potential_temperature"

  ''Examples''
atmosphere_air_water~vapor__bubble_point_temperature
atmosphere_air_water~vapor__dew_point_temperature
atmosphere_air_water~vapor__frost_point_temperature
iron__melting_point_temperature
snow__temperature
soil__temperature
water__boiling_point_temperature
water__freezing_point_temperature

* Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.
:
* Can include how measured with <assume> tags in a Model Metadata File.
:
* Note that "apparent_temperature" or "heat_index_temperature" (same as "felt_air_temperature") may be less ambiguous standard names than "heat_index", since it has units of temperature.
:
* Materials with impurities or in very small quantities may melt at a lower temperature than bulk amounts of pure material. This is quantified with [http://en.wikipedia.org/wiki/Melting-point_depression Melting-point depressions]. In the CSDMS Standard Names, these use the operation prefix "depression_of" + "melting_point_temperature".
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Critical_temperature Critical point], [http://en.wikipedia.org/wiki/Curie_point Curie point], [http://en.wikipedia.org/wiki/Dew_point_temperature Dew point], [http://en.wikipedia.org/wiki/Hydrocarbon_dew_point Hydrocarbon dew point], [http://en.wikipedia.org/wiki/Bubble_point Bubble point] and [http://en.wikipedia.org/wiki/Flash_point Flash point].
:
* See the Wikipedia pages for: [http://en.wikipedia.org/wiki/Temperature Temperature], [http://en.wikipedia.org/wiki/Equivalent_temperature Equivalent temperature], [http://en.wikipedia.org/wiki/Potential_temperature Potential temperature], [http://en.wikipedia.org/wiki/Equivalent_potential_temperature Equivalent potential temperature], [http://en.wikipedia.org/wiki/Effective_temperature Effective temperature], [http://en.wikipedia.org/wiki/Color_temperature Color temperature], [http://en.wikipedia.org/wiki/Brightness_temperature Brightness temperature], [http://en.wikipedia.org/wiki/Atmospheric_temperature Atmospheric temperature], [http://en.wikipedia.org/wiki/Sea_surface_temperature Sea surface temperature], [http://en.wikipedia.org/wiki/Convective_temperature Convective temperature], [http://en.wikipedia.org/wiki/Dry-bulb_temperature Dry-bulb temperature] and [http://en.wikipedia.org/wiki/Wet-bulb_temperature Wet-bulb temperature].

 


== {{ Bar Heading| text=Tension}} ==

  base_quantity = "tension" 
  ''Examples of Specific Quantities:'' 
  "surface_tension"

  ''Examples''

* Tension is the opposite of compression. It is often used in connection with columns, ropes and strings.
:
* Tension is not a force, but has units of force (e.g. Newtons).
:
* See: [http://en.wikipedia.org/wiki/Surface_tension Surface tension], [http://en.wikipedia.org/wiki/Tension_(physics) Tension (physics)] and [http://en.wikipedia.org/wiki/Ultimate_tensile_strength Ultimate tensile strength].

 


== {{ Bar Heading| text=Term}} ==

  base_quantity = "term" 
  ''Examples of Specific Quantities:'' 
  "acceleration_term" 
  "convection_term" 
  "diffusion_term" 
  "forcing_term" 
  "friction_loss_term" 
  "sink_term" 
  "source_term" 
  "time_derivative_term" (or use "unsteady_term" instead?)

  ''Examples''
equation~convection-diffusion__convection_term"
equation~convection-diffusion__diffusion_term"
equation~navier-stokes__body_force_term
equation~navier-stokes__convective_acceleration_term
equation~navier-stokes__pressure_gradient_term
equation~navier-stokes__unsteady_acceleration_term
equation~navier-stokes__viscosity_term (or "viscous_diffusion_term" ?)
equation~poisson__laplacian_term
equation~poisson__source_term

* Many models allow various "terms" in an equation that the model solves numerically to be saved as output.
:
* In the [http://en.wikipedia.org/wiki/Navier-Stokes Navier-Stokes equation], which is widely used for modeling fluid flow, each term has a standard name. The names are: "unsteady_acceleration_term", "convective_acceleration_term" (or "nonlinear_term"), "pressure_gradient_term" (or "pressure_term"), "viscosity_term" (or "diffusion_term" or "vector_laplacian_term") and "body_force_term".
:
* The [http://en.wikipedia.org/wiki/Convection–diffusion_equation convection-diffusion equation] has a time derivative (or unsteady) term, a diffusion term, a convection term and source term.
:
* Many of the examples above follow the '''Process_name + Quantity Pattern'''. See the top of the [[CSN_Quantity_Templates | '''CSDMS Quantity Templates''']] page and the list of [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* '''This template is still under review'''. The appropriate object_name (possibly an equation_name from the [[CSN_Assumption_Names | '''CSDMS Assumption Names''']] page) and the associated units are not entirely clear. However, this type of quantity is commonly included among a model's output variables.
:
* We may also want to include "right_hand_side" and "left_hand_side", but this is dependent on how the equation is written.
:
* See: [http://en.wikipedia.org/wiki/Field_equation Field equation], [http://en.wikipedia.org/wiki/Laplacian Laplacian], [http://en.wikipedia.org/wiki/Vector_Laplacian Vector Laplacian], [http://en.wikipedia.org/wiki/equation~poisson Poisson's equation], [http://en.wikipedia.org/wiki/Pressure_gradient Pressure gradient] and [http://en.wikipedia.org/wiki/Shallow_water_equations Shallow water equations].

 

== {{ Bar Heading| text=Thickness}} ==

  base_quantity = "thickness"

  ''Examples''
shale~burgess_stratum__thickness ("stratum" or "layer" ?)
human_hair__thickness
mars_atmosphere__thickness
model_soil_layer~0__thickness
paper__thickness

* This quantity name refers to the '''full''', top-to-bottom vertical length dimension of something that tends to cover an area that is large relative to this length.
:
* The words "depth" and "thickness" are sometimes used interchangeably. In the context of "layers", "thickness" is usually used (e.g. in meteorology, geology and hydrogeology). In the context of surface water or snow, "depth" is usually used. (As in: "How deep is the lake?" or "The lake depth is 5 meters.") The word "depth" indicates a value that is positive downward from some reference datum. There is often the connotation that it may take values less than some maximum possible value, as in "sea_water_secchi_disk_depth".
:
* See Altitude, Depth, Elevation and Height.

 


== {{ Bar Heading| text=Threshold}} ==

  operation_prefix = "threshold"

  ''Examples''

* Before 3/19/13, this was treated as a "quantity suffix" but now it is treated as an "operation prefix". In the example above, however, the word "threshold" is used as an adjective. Perhaps it should contain more information, something like "melting_point_temperature".
:
* It is more common for words like "critical" or "point" to be inserted as an adjective in front of a base quantity name to indicate a threshold value. See the template for Temperature.
:
* There is a standard name called: "snow + degree-day_threshold_temperature", but since there is no "degree-day_temperature", the name "snow + threshold_of_degree-day_temperature" doesn't make sense.

 


== {{ Bar Heading| text=Time}} ==

  quantity_suffix = "time"

  ''Examples''
channel_water__peak_time_of_volume_flow_rate
model__run_time
model__start_time
model__stop_time
model__time

* The quantity "time" can refer to the specific time associated with an event, such as "mars__local_rise_time", or to a duration, as in "relaxation_time".
:
* We may allow "time" to be used as a "quantity suffix" associated with an event like reaching a peak value. But this use case may also be handled using an operation prefix.
:
* This is commonly used in the '''Process_name + Quantity Pattern''', as in "start_time" and "stop_time". Recall that the "ing" ending of many process names is dropped. See [[CSN_Process_Names | '''CSDMS Process Names''']].
:
* In the mathematics of stochastic processes, the quantities: [http://en.wikipedia.org/wiki/Hitting_time Hitting time] and [http://en.wikipedia.org/wiki/Stopping_time Stopping time] are used.
:
* In hydrology, the terms "return time", "return period", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size. See Period.
:
* In astronomy, a "rise_time" and "set_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's [http://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services astronomical data services] page. Note that these quantities require specifying two objects.
:
* See: [http://en.wikipedia.org/wiki/Residence_time Residence time], [http://en.wikipedia.org/wiki/Relaxation_time Relaxation time], [http://en.wikipedia.org/wiki/Transition_time Transition time], [http://en.wikipedia.org/wiki/Arrival_time Arrival time] (and ETA), [http://en.wikipedia.org/wiki/Fall_time Fall time], [http://en.wikipedia.org/wiki/Lead_time Lead time], [http://en.wikipedia.org/wiki/Rise_time Rise time] and [http://en.wikipedia.org/wiki/Holding_(aviation) Holding time].
:
* See Duration and Period.

 


== {{ Bar Heading| text=Time Step}} ==

  quantity_suffix = "step" 
  base_quantity = "time" 
  "time_step" 

  ''Examples''
model__time_step

* Note that "increment" and "step" are both '''quantity suffixes''' that do not change the units of the base quantity. "Step" is usually used when the base quantity is "time".
:
* See Increment and Step.

 


== {{ Bar Heading| text=Transmittance}} ==

  base_quantity = "transmittance" 
  ''Examples of Specific Quantities:'' 
  "spectral_transmittance"

  ''Examples''
atmosphere_air_radiation~incoming~longwave__transmittance

* Transmittance is the ratio of the power per unit area [W m-2] of electromagnetic radiation '''''transmitted''''' through something to the original, '''''incident''''' power per unit area (or irradiance). It is a dimensionless number between 0 and 1.
:
* Absorptance + Reflectance + Transmittance = 1. See Absorptance and Reflectance above.
:
* Various authors recommend using the terms: Absorptivity, Emissivity, Reflectivity and Transmissivity as properties of a pure material and Absorptance, Emittance, Reflectance and Transmittance as the analogous terms for the characteristics of a specimen or sample. See: Palmer, J.M. (1994) Chapter 25: The measurement of transmission, absorption, emission and reflection, Handbook of Optics, 2nd ed., Part II, M. Bass, editor, McGraw-Hill, NY. (A PDF file is available [http://photonics.intec.ugent.be/education/ivpv/res_handbook/v2ch25.pdf '''here'''].)
:
* While "transmissivity" can mean the transmittance of a pure material (see above), it is also used for a concept in ground water hydrology.
:
* The quantity "spectral transmittance" is the transmittance associated with a specific wavelength.
:
* See: [http://en.wikipedia.org/wiki/Absorbance Absorbance], [http://en.wikipedia.org/wiki/Attenuation_coefficient Attenuation coefficient], [http://en.wikipedia.org/wiki/Beer–Lambert_law Beer-Lambert law], [http://en.wikipedia.org/wiki/Mass_attenuation_coefficient Mass attenuation coefficient], [http://en.wikipedia.org/wiki/Opacity_(optics) Opacity (optics)], [http://en.wikipedia.org/wiki/Reflectivity Reflectance] and [http://en.wikipedia.org/wiki/Transmittance Transmittance].

 


== {{ Bar Heading| text=Unit-width (and similar) Quantities}} ==

  base_quantity

  ''Examples''
human_blood_cell~red__count-per-volume
sea_surface_water_wave_crestline__power-per-length

* CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.
:
* "unit_stream_power" is somewhat similar.
:
* There are several other "per" concepts, such as:
:
* The "z_integral_of_velocity" in the CSDMS Standard Names is the same as "unit-width discharge".
:
per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width

* These could possibly be used as adjective or modifier prefixes for a base quantity.

 


== {{ Bar Heading| text=Velocity}} ==

  base_quantity = "speed" 
  ''Examples of Specific Quantities:'' 
  "darcy_speed" 
  "drift_speed" 
  "escape_speed" 
  "fall_speed" 
  "flow_speed" 
  "group_speed" 
  "impact_speed" 
  "initial_speed" 
  "phase_speed" (also called "celerity") 
  "settling_speed" 
  "terminal_fall_speed" 
:
  base_quantity = "velocity" 
  ''Examples of Specific Quantities:'' 
  "darcy_velocity" 
  "drift_velocity" 
  "group_velocity" 
  "impact_velocity" 
  "initial_velocity" 
  "phase_velocity" (vector field of wave rays) 
  "shear_velocity" (also called "friction velocity") 
:
  "azimuth_angle_of_velocity" 
  "elevation_angle_of_velocity" 
  "x_component_of_velocity" 
  "y_component_of_velocity" 
  "z_component_of_velocity"

  ''Examples''
atmosphere_ball__fall_speed
atmosphere_ball__terminal_fall_speed ### (air_ball__** sounds strange)
earth__escape_speed (vs. escape_velocity)
electron__drift_speed
water_sand_grain__settling_speed # (sand grain in water)

electron__x_component_of_drift_velocity
electron__y_component_of_drift_velocity

sea_water_flow__east_component_of_velocity
sea_water_flow__north_component_of_velocity
sea_water_flow__up_component_of_velocity
sea_water_flow__speed
sea_water_flow__x_component_of_velocity
sea_water_flow__y_component_of_velocity

sea_water_wave~internal~gravity__group_speed
sea_water_wave~internal~gravity__phase_speed
sea_surface_water_wave__group_speed ## wave~gravity ??
sea_surface_water_wave__phase_speed

soil_water_flow__x_component_of_darcy_velocity
soil_water_flow__y_component_of_darcy_velocity

sea_surface_air_flow__magnitude_of_shear_velocity
sea_surface_air_flow__x_component_of_shear_velocity
sea_surface_air_flow__y_component_of_shear_velocity

* Velocity is a vector quantity with a magnitude and a direction. Most models store the components of a velocity field as separate variables, in which case the operation '''component_of''' can be used as shown in the example above. (See the template for Component.) However, it is also possible that one model would request a complete vector field (i.e. all components) from another model as a single "quantity". Because of this, we need to allow "velocity" itself (a vector) as a base quantity name.
:
* In addition to the "component_of" operation, there are several other operations that can be used to identify an attribute of a vector, such as: "magnitude_of", "azimuth_angle_of" and "elevation_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the elevation angle (from spherical coordinates) is also required. See the [[CSN_Operation_Templates | '''CSDMS Operation Templates]].
:
* The quantity name '''darcy_velocity''' is used for 3D flow of water in soil to emphasize its macroscopic definition as a volume flux or "specific discharge". See the template for Attributes of Soil.
:
* The magnitude of the '''shear_velocity''' is defined as the square root of the shear stress (at a boundary) divided by the mass density. It is also called the "friction velocity". Shear velocity is a vector quantity, and its direction is the same as the shear stress component used to define it.
:
* The shorter quantity name "speed" is used in CSDMS standard names instead of "magnitude_of_velocity" but they mean the same thing. See Speed.
:
* The terms [http://en.wikipedia.org/wiki/Shear_velocity shear velocity], [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] and [http://en.wikipedia.org/wiki/Escape_velocity escape velocity] are all used but they each refer to a speed, or velocity magnitude. The "escape_speed" for Earth is a scalar quantity, independent of direction.
:
* Note that [http://en.wikipedia.org/wiki/Terminal_velocity terminal velocity] (called "terminal_fall_speed" here) is a quantity that requires two objects to be specified, an object and the fluid through which it is falling. The '''Object-in-object Pattern''' is therefore used. In the context of a particle falling through water, the term "settling velocity" (called settling_speed here) is commonly used.
:
* See: [http://en.wikipedia.org/wiki/Angular_velocity Angular velocity], [http://en.wikipedia.org/wiki/Drift_velocity Drift velocity], [http://en.wikipedia.org/wiki/Flow_velocity Flow velocity], [http://en.wikipedia.org/wiki/Group_velocity Group velocity], [http://en.wikipedia.org/wiki/Phase_velocity Phase velocity], [http://en.wikipedia.org/wiki/Proper_velocity Proper velocity], [http://en.wikipedia.org/wiki/Relative_velocity Relative velocity], [http://en.wikipedia.org/wiki/Soil_mechanics Soil mechanics] (Darcy velocity) [http://en.wikipedia.org/wiki/Stokes_drift Stokes drift] and [http://en.wikipedia.org/wiki/Velocity Velocity].
:
* See the template for Speed.

 


== {{ Bar Heading| text=Viscosity}} ==

  base_quantity = "viscosity" 
  ''Examples of Specific Quantities:'' 
  "apparent_viscosity" 
  "dynamic_shear_viscosity" 
  "dynamic_volume_viscosity" 
  "eddy_viscosity" 
  "extensional_viscosity" 
  "kinematic_shear_viscosity" 
  "kinematic_volume_viscosity" 

  ''Examples''
air__dynamic_shear_viscosity
air__dynamic_volume_viscosity
air__kinematic_shear_viscosity
air__kinematic_volume_viscosity
polymer__extensional_viscosity
sea_water__eddy_viscosity
water__dynamic_shear_viscosity
water__dynamic_volume_viscosity
water__kinematic_shear_viscosity
water__kinematic_volume_viscosity
water__x_z_component_of_viscosity

* Viscosity is a tensor quantity and is decomposed into "shear" and "volume" components that are analogous to the "shear" and "normal" components used for stress, another tensor quantity. "bulk viscosity" is a synonym for [http://en.wikipedia.org/wiki/Volume_viscosity volume viscosity] which is important for compressible fluids but is less well-known than shear viscosity.
:
* Since viscosity is really a tensor, we can refer to each of its possible components using the "component_of" operation; e.g. "x_z_component_of_viscosity".
:
* Viscosity depends on temperature, so a reference temperature should be provided with an <assume> tag in a Model Metadata File. For an ideal gas, Sutherland's formula gives dynamic viscosity as a power-law function of temperature. For a dilute gas, the [http://en.wikipedia.org/wiki/Chapman-Enskog_theory Chapman-Enskog] equation can be used. For liquids, several different models are available; see: [http://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity Temperature dependence of liquid viscosity].
:
* Kinematic viscosity is just the dynamic viscosity divided by the density of the fluid. It is used in the definition of the [http://en.wikipedia.org/wiki/Reynolds_number Reynolds number].
:
* "The "eddy viscosity" concept is used to parameterize small-scale details in models of turbulent flow. It is sometimes contrasted with "molecular viscosity". Also see the Diffusivity template.
:
* The reciprocal of viscosity is called ''fluidity''.
:
* See: [http://en.wikipedia.org/wiki/Apparent_viscosity Apparent viscosity], [http://en.wikipedia.org/wiki/Viscosity Viscosity], [http://en.wikipedia.org/wiki/Inviscid_flow Inviscid flow], [http://en.wikipedia.org/wiki/Large_eddy_simulation Large eddy simulation (LES)], [http://en.wikipedia.org/wiki/Newtonian_fluid Newtonian fluid], [http://en.wikipedia.org/wiki/Non-Newtonian_fluid Non-Newtonian fluid] and [http://en.wikipedia.org/wiki/Volume_viscosity Volume viscosity].

 


== {{ Bar Heading| text=Voltage}} ==

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  ''Examples''
battery__voltage
appliance~electric__voltage
fence~electric__voltage

* See: [http://en.wikipedia.org/wiki/Voltage Voltage] and [http://en.wikipedia.org/wiki/Voltage_drop Voltage drop].

 

== {{ Bar Heading| text=Vorticity}} ==

  base_quantity = "vorticity" 
  ''Examples of Specific Quantities:'' 
  "absolute_vorticity" 
  "ertel_potential_vorticity" ### (a scalar quantity) 
  "planetary_vorticity" 
  "potential_vorticity" 
  "relative_vorticity"

  ''Examples''
sea_water_flow__down_component_of_vorticity
sea_water_flow__east_component_of_vorticity
sea_water_flow__magnitude_of_vorticity
sea_water_flow__north_component_of_vorticity
sea_water_flow__south_component_of_vorticity
sea_water_flow__up_component_of_vorticity
sea_water_flow__west_component_of_vorticity
sea_water_flow__x_component_of_vorticity
sea_water_flow__y_component_of_vorticity
sea_water_flow__z_component_of_vorticity

* Vorticity is a vector quantity defined as the curl of a fluid velocity (vector) field. The quantity name for a component of the vorticity vector uses the "component_of" operation prefix as shown in the examples above. See the Component template.
:
* '''''Relative vorticity''''' is the vorticity of air velocity relative to the Earth. When "vorticity" appears without an adjective, relative vorticity with respect to a fixed coordinate system is assumed. See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Relative vorticity].
:
* '''''Absolute vorticity''''' is "relative vorticity" plus "planetary vorticity". See: [http://en.wikipedia.org/wiki/Vorticity#Atmospheric_sciences Absolute vorticity].
:
* '''''Planetary vorticity''''' is the vorticity associated with the rotation of the Earth.
:
* '''''Potential vorticity''''' is absolute vorticity divided by the vertical spacing between levels of constant entropy. It seems that there are two types of potential vorticity. Ertel's potential vorticity (ertel_potential_vorticity) is a scalar quantity, defined as a dot product of absolute vorticity and the gradient of potential temperature. See: [http://en.wikipedia.org/wiki/Potential_vorticity Potential vorticity].
:
* Here, "flow" is used as a shorthand for "flow_field" in the object part of the name. This is an example of the Object Name + Model Name Pattern.
:
* Since the curl of any gradient vector is zero, taking the curl of the [http://en.wikipedia.org/wiki/Navier-Stokes_equations Navier-Stokes equation] eliminates the pressure gradient term.
:
* See [http://en.wikipedia.org/wiki/Vorticity Vorticity], [http://en.wikipedia.org/wiki/Circulation_(fluid_dynamics) Circulation] and [http://en.wikipedia.org/wiki/Vector_calculus_identities Vector calculus identities].

 


== {{ Bar Heading| text=Wavelength}} ==

  base_quantity = "wavelength" 
  ''Examples of Specific Quantities:'' 
  "compton_wavelength" 
  "reduced_compton_wavelength"

  ''Examples''
electron__compton_wavelength
sea_water_wave~internal~gravity__wavelength (### or sea_internal_water_wave ??)
sea_surface_water_wave__wavelength
wave~airy__wavelength
wave~cnoidal__wavelength
wave~sine__wavelength
wave~stokes__wavelength

* The wavelength is the distance between successive crests or troughs in a periodic function.
:
* See the section called Attributes of Radiation above.
:
* See: [http://en.wikipedia.org/wiki/Amplitude Amplitude], [http://en.wikipedia.org/wiki/Angular_frequency Angular frequency], [http://en.wikipedia.org/wiki/Compton_wavelength Compton wavelength], [http://en.wikipedia.org/wiki/De_Broglie_wavelength de Broglie wavelength], [http://en.wikipedia.org/wiki/Frequency Frequency] (and Period), [http://en.wikipedia.org/wiki/Hertz Hertz], [http://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength Thermal de Broglie wavelength], [http://en.wikipedia.org/wiki/Wavelength Wavelength], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 

== {{ Bar Heading| text=Wavenumber}} ==

  base_quantity = "wavenumber"

  ''Examples''
sea_surface_water_wave__wavenumber
wave~airy__wavenumber
wave~cnoidal__wavenumber
wave~electromagnetic__wavenumber
wave~seismic__wavenumber
wave~stokes__wavenumber

* "Wavenumber" is a basic property of a periodic function or waveform, along with amplitude and wavelength. It can be understood as a '''spatial frequency''', in contrast to just ''frequency'', which refers to a '''temporal frequency'''. Both wavenumber and frequency can be preceded with the word "angular" to define a different, but related quantity. See ''Frequency'' above.
:
* The phase speed of a wave is equal to ratio of the wavelength and period. It is also equal to the ratio of the angular frequency and angular wavenumber.
:
* A [http://en.wikipedia.org/wiki/Dispersion_relation ''dispersion relation''] is a relationship between the wavenumber and frequency that is determined by the specific physics of a wave propagation problem.
:
* See [http://en.wikipedia.org/wiki/Dispersion_relation Dispersion relation], [http://en.wikipedia.org/wiki/Wavenumber Wavenumber] and [http://en.wikipedia.org/wiki/Wave_vector Wave vector].

 


== {{ Bar Heading| text=Weight}} ==

  base_quantity = "weight" 
  ''Examples of Specific Quantities:'' 
  "volume-specific_weight"

  ''Examples''
bear~alaskan~black__weight

* The weight of an object has units of force and is the product of its mass and the standard gravity constant for the planet on which the weight is being measured. (It actually even depends on distance above the planet's surface.) Because of this, perhaps we should use quantity names like "earth-weight" (or even "earth-surface-weight") and "mars-weight", etc.
:
* We could use "weight-per-volume" instead of "specific_weight".
:
* What about "submerged weight" ?
:
* See: [http://en.wikipedia.org/wiki/Specific_weight Specific weight] and [http://en.wikipedia.org/wiki/Weight Weight].

 


== {{ Bar Heading| text=Work}} ==

  base_quantity = "work" 
  ''Examples of Specific Quantities:'' 
  ""

  ''Examples''

* Work has units of energy and measures a change in energy due to a force being applied to an object over a distance.
:
* See: [https://en.wikipedia.org/wiki/Work_(physics) Work (physics)].

 


== {{ Bar Heading| text=Yield}} ==

  base_quantity = "yield" 
  ''Examples of Specific Quantities:'' 
  "specific_yield" (in groundwater modeling)

  ''Examples''
basin_outlet_sediment__yield

* In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a drainage basin over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: [http://en.wikipedia.org/wiki/River#Sediment_yield sediment yield].
:
* In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: [http://en.wikipedia.org/wiki/Crop_yield Crop yield] and [http://en.wikipedia.org/wiki/Yield_(wine) Yield (wine)].
:
* What about "yield_strength" (plastic deformation) ? See: [http://en.wikipedia.org/wiki/Yield_(engineering) Yield (engineering)].
:
* See also: [http://en.wikipedia.org/wiki/Specific_yield#Specific_yield Specific yield] (groundwater), [http://en.wikipedia.org/wiki/Yield_(chemistry) Yield (chemistry)], [http://en.wikipedia.org/wiki/Yield_surface Yield surface] and [http://en.wikipedia.org/wiki/Quantum_yield Quantum yield].

:
:
: