CSN Quantity Templates

  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: 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.

• Each template includes examples and explanatory notes, and many of them make reference to the CF Standard Names, sometimes using the abbreviation "CF".

• Quantity seems to be the best word choice here, see Quantity and 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 CSDMS Operation Templates.) For example, "eastward_velocity_component" can be expressed as "eastward_component_of_velocity". As an operation prefix, additional adjectives can be applied for clarity (when necessary) without losing parsability, as in "eastward_downward_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: CSDMS Operation Templates.

• Process_name + Quantity Pattern. Many quantity names contain a process name modifier from the standardized list of 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_rate

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_visible-light__speed  ## (possibly)
atmosphere_carbon-dioxide__partial_pressure
atmosphere_carbon-dioxide__relative_saturation
atmosphere_water__dew_point_temperature
atmosphere_water__precipitation_rate
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_on_rubber__kinetic_friction_coefficient
pavement_on_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:

brain_to_body__mass_ratio
earth_to_mars__travel_time
earth_to_sun__mean_distance
 
carbon_to_hydrogen__bond_length
hydrogen_to_oxygen__bond_energy (See: 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__net_shortwave_radiation_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_cross-section__width_to_depth_ratio
electron__charge_to_mass_ratio    charge to mass ratio
electron__mass_to_charge_ratio
watershed_outlet__bankfull-width_to_depth_ratio
watershed_outlet_water__width_to_depth_ratio

Note that "hydraulic radius" is a valid quantity name, but could also be expressed as "channel_cross-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_opposite_of_gradient_of_elevation   (relative to a fixed axis)
density    = mass_to_volume_ratio   (but density sometimes has other meanings; use "mass_density" ??)
discharge  = 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" quantities. 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". Examples include:

atmosphere_top-surface__outgoing_longwave_radiation_flux
atmosphere_top-surface__incoming_shortwave_radiation_flux
lake_water__incoming_volume_flow_rate
lake_water__outgoing_volume_flow_rate
land_surface__net_longwave_radiation_flux   (net = incoming - outgoing)
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".

Affinity

  base_quantity = "affinity"
  quantity = "chemical_affinity"
  quantity = "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 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 Chemical affinity, Electron affinity and Desiccant.

Altitude

  base_quantity = "altitude"

  Examples

airplane__altitude
balloon__altitude
projectile__altitude
skydiver__altitude

• 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-seafloor_altitude" ??

• 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: Altitude above ground level, Elevation, Height above average terrain (HAAT), Lowest safe altitude and Mean sea level.

• See the Elevation template.

Angle

  base_quantity = "angle"

  Examples

azimuth_angle, bank_angle, bond_angle, camber_angle, caster_angle, declination_angle,
flaring_angle, friction_angle, incidence_angle, inclination_angle,  pitch_angle, polarization_angle,
rake_angle, repose_angle, roll_angle, rotation_angle, scattering_angle, shock_angle, slope_angle,
spreading_angle, tilt_angle, torsion_angle, yaw_angle, zenith_angle

• 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 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: 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: 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.

• A few terms sound strange in this form, like "repose_angle", instead of "angle_of_repose". But this doesn't pose any real problem.

• 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".

• The local azimuth and zenith angles that can be associated with a 2D or 3D vector field are treated as operations. See the CSDMS Operation Templates for more information.

• 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: Camber angle and Caster angle (or Rake angle).

• Three 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".

• See: Flaring angle.. It 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: Aspect (geography), Orbital inclination and Slope.

Anomaly

  operation_prefix = "anomaly_of"

  Examples

air__anomaly_of_pressure
air__anomaly_of_temperature
sea_surface__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

Area

  base_quantity = "area"
  quantity = "drainage_area"
  quantity = "surface_area"

  Examples

channel_cross-section__area
channel_cross-section__wetted_area
glacier_surface__area
lake_surface__area
sphere_surface__area
watershed__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 watershed, such as "drainage area", "contributing area", "upstream contributing area", "total contributing area (TCA)" and "specific contributing area (SCA)". A watershed 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 the object is watershed, there is no need to distinguish between "watershed_area" and "watershed_drainage_area", so "drainage" is dropped.

• 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.

Attributes of Atoms

  quantity = attribute
  quantity = "atomic_mass"
  quantity = "emission_frequency"
  quantity = "relative_atomic_mass" (dimensionless ratio to carbon-12)
  quantity = "mass_number" (number of protons + neutrons)
  quantity = "neutron_number" (number of neutrons)
  quantity = "proton_number" (number of protons)

  Examples

carbon_isotope__neutron_number  (use "isotope" like this ??)
cesium_atom__mass_number
cesium_atom__neutron_number
cesium_atom__proton_number
cesium_atom__relative_atomic_mass

• There is controversy over the term "atomic_weight" and the term "relative_atomic_mass" seems preferably and more precise.

• While "atomic number" is a standard term, the synonym "proton_number" is winning favor because it is more specific and because "neutron_number" is also used.

• A specific frequency in the emission spectrum of cesium-133 is used for the ISU definition of the "second", so cesium is used in atomic clocks. It is not really a characteristic vibration frequency of the atom. (But molecules do have vibration frequencies; see Attributes of Molecules below.) It is a transition or resonance frequency between two hyperfine ground states of cesium-133. A CSDMS standard name for this frequency could be something like: "cesium-133_isotope_state1_to_state2_hyperfine_transition_frequency", where "state1" and "state2" would be replaced with appropriate names for the two states involved.

• See the CSDMS Object Template for Atoms, Compounds, Ions and Molecules below for more information.

Attributes of Channels

  quantity = attribute
  object = "channel_bank"
  object = "channel_bank_water"
  object = "channel_bed"
  object = "channel_bed_grain"
  object = "channel_bed_surface"
  object = "channel_centerline"
  object = "channel_cross-section"
  object = "channel_end-to-end-line"
  object = "channel_entrance"
  object = "channel_exit"
  object = "channel_water"
  object = "channel_water_suspended-sediment"
  object = "channel_water_surface"

  Examples

channel_bank_water__volume-per-length_flow_rate  (or volume-per-unit-length ??)
 
channel__bankfull_width
channel__downstream_hydraulic_geometry_depth_vs_discharge_exponent
channel__downstream_hydraulic_geometry_slope_vs_discharge_coefficient
channel__station_hydraulic_geometry_width_vs_discharge_exponent
channel__meander_amplitude
channel__meander_curvature_radius
channel__meander_wavelength
 
channel_bed__manning_coefficient
channel_bed__relative_roughness_ratio     (a dimensionless ratio)
channel_bed__roughness_length
 
channel_bed_grain__d50_diameter
channel_bed_grain__d84_diameter
 
channel_bed_surface__cross-stream_slope
channel_bed_surface__downstream_slope
 
### channel__bed_roughness_length_to_water_depth_ratio    ????
 
channel_bed_water__hydrostatic_pressure
channel_bed_water__pressure  (assumed "dynamic" if not hydrostatic ?)
channel_bed_water__shear_stress
 
channel_centerline__length
channel_centerline__straight_sinuosity  (same as "tortuosity" ??)
channel_centerline__valley_sinuosity
 
channel_centerline_endpoints__difference_of_elevation
channel_centerline_endpoints__separation_distance    (also called: "chord length")
 
channel_cross-section__area
channel_cross-section__hydraulic_radius
channel_cross-section__max_of_depth
channel_cross-section__perimeter
channel_cross-section__wetted_area
channel_cross-section__wetted_perimeter
channel_cross-section__width-to-depth_ratio
 
channel_cross-section_top__width

channel_cross-section_trapezoid_side__flaring_angle  (or bank_angle or spreading_angle ??)
channel_cross-section_trapezoid_bottom__width

channel_entrance_center__elevation
channel_entrance_center__latitude 
channel_entrance_center__longitude
channel_entrance__specific_contributing_area
channel_entrance__total_contributing_area    (or drainage area ?)
   
channel_exit_center__elevation
channel_exit_center__latitude
channel_exit_center__longitude
channel_exit__specific_contributing_area
channel_exit__total_contributing_area
 
channel_water__darcy_friction_factor  
channel_water__mass-per-volume_density
channel_water__depth_and_bed_slope_product    # (product is a quantity suffix)
channel_water__fanning_friction_factor
channel_water__froude_number
channel_water__max_of_depth
channel_water__depth
channel_water__shear_stress (anywhere in the channel, vs. at channel_bed)
channel_water__speed   (or flow_speed ??)
channel_water__pressure     (anywhere in the channel vs. at channel_bed)
channel_water__temperature
channel_water__volume
channel_water__volume_flow_rate     (i.e. "Q" or discharge)
channel_water__volume_flow_rate_law_area_exponent
channel_water__volume_flow_rate_law_coefficient
channel_water__volume-per-unit-width_flow_rate  (i.e. "q", or unit-width discharge)
channel_water__incoming_volume_flow_rate     (or channel_entrance_water__volume_flow_rate ??)
channel_water__outgoing_volume_flow_rate     (or channel_exit_water__volume_flow_rate ??)
 
channel_water_surface__cross-stream_slope
channel_water_surface__downstream_slope
 
channel_water_suspended-sediment__mass_concentration
 
channel_water_total-sediment__volume_flow_rate  (i.e. "Qs" or "sediment discharge")
channel_water_total-sediment__volume_flow_rate_law_area_exponent
channel_water_total-sediment__volume_flow_rate_law_coefficient
channel_water_total-sediment__volume_flow_rate_law_slope_exponent
 
land_surface_water__volume-per-unit-contour-length_flow_rate  (i.e. "q" or "unit width discharge")

• Note that "entrance" and "exit" are used instead of "high_end" and "low_end" because it is possible for the "exit" to be the "high end".

• Instead of "channel_entrance__contributing_area", we could use: "channel_entrance_watershed__area". There are several different methods for computing contributing area (or drainage area) and the method should be indicated using an <assume> tag in a Model Metadata File, such as "d8_flow_direction_method", "d_infinity_flow_direction_method" or "mass_flux_flow_direction_method".

• It appears that Howard (1980) may have been the first to parameterize sediment discharge as Qs = K * A^m * S^n, where A is contributing area and S is channel slope. (Or perhaps Carson and Kirkby or Kirkby were first.) If so, then we could use the standard names:

channel_water_total-sediment__howard_law_coefficient  (K)
channel_water_total-sediment__howard_law_area_exponent (m)
channel_water_total-sediment__howard_law_slope_exponent (n)

Note that "geomorphic_transport_law" could also be used but is more general than "howard_law".

• It would be nice to have a short, unambiguous standard name for:
  channel_entrance-to-exit__difference_of_elevation.
  Perhaps we could introduce "drop" as a quantity suffix (like increment and step) for this purpose, but this doesn't capture the end-to-end aspect of the drop.

• Note that "channel_bank_angle" by itself would be ambiguous; is it the angle the bank makes with the vertical z-axis or with a horizontal x-axis? However, "channel_cross_section_trapezoid_bank_angle" is clear.

• A quantity like "bottom_width" or "bank_angle" may only be well-defined for cross-sections of a particular shape, like a trapezoid. In such cases we use the Object_name + model_name Pattern.

• Avoid inserting the word "mean" or "average" for quantities like "depth" and "speed". Assumptions or clarifications on how quantities are computed are provided using <assume> tags in an associated Model Metadata File.

• We talk of "channel_networks", but the network is not part of the channel.

• An outlet would be considered part of a watershed and not part of a channel. See the object pattern for Watershed, Basins and Catchments.

Attributes of Earthquakes

  quantity = attribute
  object = earthquake
  object = earthquake_auxiliary-plane
  object = earthquake_epicenter
  object = earthquake_fault
  object = earthquake_fault_plane
  object = earthquake_fault_plane_asperity
  object = earthquake_foot-wall-block
  object = earthquake_hanging-wall-block
  object = earthquake_hypocenter
  object = earthquake_p-wave
  object = earthquake_s-wave
  object = earthquake_shadow-zone
  object = earthquake_station
  object = earthquake_swarm
 
  object = seismic_wave

  Examples

earthquake__count      (number of earthquakes, or N in Gutenberg-Richter law)
earthquake__critical_slip_distance
earthquake__duration   (overall duration of the event)
earthquake__drop_of_dynamic_stress   ????
earthquake__drop_of_static_stress  ???
earthquake__east_component_of_slip-vector
earthquake__gutenberg-richter_law_a_parameter
earthquake__gutenberg-richter_law_b_parameter
earthquake__modified_mercali_intensity      (for ground motion instead ??)
earthquake__modified_omori_law_c_parameter
earthquake__modified_omori_law_k_parameter
earthquake__modified_omori_law_p_parameter
earthquake__magnitude_of_moment_tensor    ### (Same as "moment_magnitude" ?)
earthquake__moment_magnitude              ### (Same as "magnitude_of_moment_tensor" ?)
earthquake__moment_tensor
earthquake__north_component_of_slip-vector
earthquake__origin_time
earthquake__radiated_seismic_energy   (measured by seismometers.  How does this compare to release_energy ??)
earthquake__release_energy      (same as the "seismic moment" ??)
earthquake__richter_magnitude
earthquake__rupture_speed     (or rupture_velocity ??)
earthquake__seismic_moment_energy     (or just seismic_moment ??  moment = Force x distance,  [Newton meters = Joules]
earthquake__slip_angle           (angle between slip vector and horizontal)
earthquake__slip_distance
earthquake__slip_duration     (also known as the "rise time", as seen on a seismograph, from rupture time to peak moment release.)
earthquake__slip_speed    (slip is a 2D vector)
 
earthquake__east_east_component_of_moment_tensor       (notation Mpp;  r = up, p = east, t = south; tensor is symmetric)
earthquake__east_up_component_of_moment_tensor         (notation Mpr)
earthquake__south_east_component_of_moment_tensor      (notation Mtp)
earthquake__south_south_component_of_moment_tensor     (notation Mtt)
earthquake__up_south_component_of_moment_tensor        (notation Mrt)
earthquake__up_up_component_of_moment_tensor           (notation Mrr)
 
earthquake_auxiliary-plane__**
  
earthquake_epicenter__elevation
earthquake_epicenter__latitude       (equal to the earthquake_hypocenter__latitude)
earthquake_epicenter__longitude      (equal to the earthquake_hypocenter__longitude)
 
earthquake_fault__length
 
earthquake_fault_plane__dip_angle   (angle between fault plane and horizontal)
earthquake_fault_plane__length
earthquake_fault_plane__rake_angle  (direction that hanging wall block moves from, measured on the fault plane)
earthquake_fault_plane__rupture_area
earthquake_fault_plane__rupture_length
earthquake_fault_plane__rupture_time    (time that rupture event begins)
earthquake_fault_plane__rupture_width
earthquake_fault_plane__slip-rake_angle   ???
earthquake_fault_plane__strike_angle  (angle in plane of Earth's surface
earthquake_fault_plane__width
 
earthquake_fault_plane_asperity__contact_area   (perhaps 0.22 times the fault plane rupture_area ??)
 
earthquake_foot-wall-block__**
earthquake_hanging-wall-block__**
 
earthquake_hypocenter__depth      (hypocenter is also called the "focus")
earthquake_hypocenter__latitude
earthquake_hypocenter__longitude
earthquake_hypocenter-to-station__distance
 
earthquake_p-wave__amplitude    ## (p = primary, pressure or push-pull)
earthquake_p-wave__frequency
earthquake_p-wave__period
earthquake_p-wave__speed
earthquake_p-wave__takeoff_angle          (angle from the vertical of a seismic ray as it leaves the focus)
earthquake_p-wave__wavelength
earthquake_p-wave_station__arrival_time
earthquake_p-wave_station__travel_time
  
earthquake_s-wave__amplitude   ## (s = secondary, shear or shake)
earthquake_s-wave__frequency
earthquake_s-wave__period
earthquake_s-wave__speed
earthquake_s-wave__takeoff_angle          (angle from the vertical of a seismic ray as it leaves the focus)
earthquake_s-wave__wavelength
earthquake_s-wave_station__arrival_time
earthquake_s-wave_station__travel_time
 
earthquake_seismograph__shaking_amplitude    (is this an attribute of a seismograph ?)
  
earthquake_station__elevation
earthquake_station__latitude
earthquake_station__longitude

• Seismic moment = M0 = shear_modulus (rigidity) x slip_distance (displacement) x rupture_area. Units of energy and sometimes called "seismic moment energy".

• Moment magnitude = Mw = (2/3) log10( M0 ) - 6.0 [dimensionless].

• Should we use "aki_moment_tensor" for clarity instead of just "moment_tensor", after Aki (1972) ??

• The "takeoff_angle" and "azimuth_angle" give the direction in which a seismic (wave) ray leaves the focus or hypocenter.

• Seismic wave travel times are from source to station.

• How are the following terms defined? rupture azimuth, source duration, apparent source duration, particle velocity, static stress drop, dynamic stress drop, radiated seismic energy, rupture top depth, rupture down dip width?

• Some mathematical earthquake models are the Burridge-Knopoff (1D spring-block or "slider-block") model (and variants) and the Olami-Feder-Christensen model.

• There are many types of Seismic waves, including body waves, such as: P-waves and S-waves and surface waves, such as: Love waves, Rayleigh waves, and Stonely waves.

• See: Bulk modulus, Compressibility, Elastic modulus, Shear modulus, Stiffness and Young's modulus.

• See: Earthquake, Earthquake rupture, Earthquake swarm, Epicenter, Fault (geology), Focal mechanism, Gutenberg-Richter Law, Hypocenter (also called the "focus"), Mercali intensity scale, Moment magnitude scale, Richter magnitude scale, Seismic moment, Seismic scale, Seismic wave, Strike and dip and Shadow zone.

• Also see the section called: Attributes of Planets.

Attributes of Glaciers

  quantity = attribute

  Examples

glacier_ablation-zone__area
glacier_ablation-zone__area_fraction   (or ablation_zone_to_total_area_fraction ?)
 
glacier_accumulation-zone__area
glacier_accumulation-zone__area_fraction
 
glacier_equilibrium-line__altitude   ## (vs. elevation in this case)
 
glacier_bed__eastward_downward_component_of_shear_stress
glacier_bed__magnitude_of_shear_stress
glacier_bed__northward_downward_component_of_shear_stress
glacier_bed__pressure   # (hydrostatic or dynamic ??)
glacier_bed__sliding_speed
glacier_bed__x_z_component_of_shear_stress
glacier_bed__y_z_component_of_shear_stress
 
glacier_bed_surface__aspect_angle
glacier_bed_surface__slope       (See: Surface template.)
glacier_bed_surface__slope_angle
 
glacier__azimuth_angle_of_flow_velocity
glacier__downward_component_of_flow_velocity
glacier__eastward_component_of_flow_velocity
glacier__northward_component_of_flow_velocity
glacier__southward_component_of_flow_velocity
glacier__westward_component_of_flow_velocity
glacier__x_component_of_flow_velocity
glacier__y_component_of_flow_velocity
glacier__z_component_of_flow_velocity
glacier__zenith_angle_of_flow_velocity
 
glacier__flow_speed
glacier__glen_law_coefficient      ## (or "creep_parameter" ?)
glacier__glen_law_exponent       ## (or "creep_exponent" ?)
glacier__internal_temperature
glacier__mass
glacier__melt_rate
glacier__thickness
glacier__time_derivative_of_thickness
glacier__time_integral_of_melt_rate      # (cumulative meltwater volume)
glacier__volume
  
glacier_terminus__calving_rate
glacier_terminus__retreat_rate      (See: Glacier retreat; perhaps a terminus speed)
glacier_terminus_left-side__latitude   #### (for left-side, need to specify if looking downstream or upstream)
glacier_terminus_left-side__longitude
glacier_terminus_right-side__latitude
glacier_terminus_right-side__longitude
  
glacier_top_surface__area
glacier_top_surface__aspect_angle
glacier_top_surface__emissivity
glacier_top_surface__incoming_longwave_radiation_flux
glacier_top_surface__incoming_shortwave_radiation_flux
glacier_top_surface__outgoing_longwave_radiation_flux
glacier_top_surface__slope       (see glacier_bed_surface_slope)
glacier_top_surface__slope_angle
glacier_top_surface__temperature    ### (or just glacier_top__temperature ??)
 

• In glaciology, "mass_balance" has a specific meaning that can be confusing to scientists from other disciplines. See: Glacier mass balance. It is the difference between accumulation and ablation (melting and sublimation) and therefore the net rate at which ice is being "added" to the glacier. The quantity name: "glacier__time_derivative_of_thickness" is unambiguous (it avoids domain-specific terms) and is more consistent with other standard names.

• Within the CSDMS Standard Names, quantity names "altitude" and "elevation" are taken to have distinct meanings. See Altitude and Elevation. However, the quantity name equilibrium_line_altitude is allowed since it is a standard term in glaciology and otherwise follows the naming rules.

• Note that these names don't contain the word "ice", since a glacier is a persistent body of ice (by definition) and including "ice" is therefore redundant. However, for a glacier on another planet (e.g. Mars) that is not made of water, an adjective such as "carbon_dioxide" can be inserted before "glacier". In fact, this is the trend in the current literature.

• We may need an additional adjective before "area" in order to distinguish between a "surface area" and "projected area".

• See: Accumulation zone, Ablation zone, Glacier, Ice sheet, Meltwater and Glacier terminus.

Attributes of Materials

  quantity = attribute
  quantity = "lame_parameter"
  quantity = "bulk_modulus"
  quantity = "poisson_ratio"
  quantity = "shear_modulus"

  Examples:

earth_material__poisson_ratio
earth_material__shear_modulus

• See: Materials science and Poisson ratio.

Attributes of Models

  quantity = attribute

  Examples

model_grid__column_count   # (number of columns)
model_grid__row_count  # (number of rows)
 
model_grid_east-edge__longitude
model_grid_north-edge__latitude
model_grid_south-edge__latitude
model_grid_west-edge__longitude
 
model_grid_cell__area
model_grid_cell__column_index
model_grid_cell__d8_total_contributing_area
model_grid_cell__d8_flow_length
model_grid_cell__d8_flow_width
model_grid_cell__d8_slope
model_grid_cell__d_infinity_total_contributing_area
model_grid_cell__d_infinity_slope
model_grid_cell__diameter
model_grid_cell__perimeter
model_grid_cell__row_index
model_grid_cell__row-major-offset_index
model_grid_cell__total_contributing_area   #####
  
model_grid_cell_center__latitude
model_grid_cell_center__longitude
 
model_grid_cell_east-edge__longitude
model_grid_cell_west-edge__longitude
model_grid_cell_south-edge__latitude
model_grid_cell_north-edge__latitude
 
model_grid_cell_east-edge__length
model_grid_cell_west-edge__length
model_grid_cell_south-edge__length
model_grid_cell_north-edge__length
model_grid_cell_x-edge__length
model_grid_cell_y-edge__length
 
model_grid_cell_water__time_derivative_of_volume
model_grid_cell_water__incoming_volume_flow_rate
model_grid_cell_water__outgoing_volume_flow_rate
 
model_soil_layer-0__porosity
model_soil_layer-0__thickness
model_soil_layer-0__wetted_thickness
 
model__run_time
model__start_time
model__stop_time
model__time
model__time_step

• A model of a physical process will typically discretize both the spatial domain and time. This introduces several quantities that do not exist in the "real world", but only within the context of the model, as shown in the examples above. Note that "total_contributing_area" is a quantity that is technically associated with a segment of a contour line, but is typically attributed to a grid cell.

• While CSDMS component models often request variables from one another (i.e. a model tells the framework it needs a variable using the BMI function get_output_var_names()), CSDMS does not support (and discourages) models requesting model attributes from one another. Model attributes (i.e. output variables that start with the word "model") that are listed among a model's output variables are only intended for use by the modeling framework. Part of the CSDMS philosophy is the idea that model components should not need to know anything about the internal details of other models that they want to obtain output variables from --- this is viewed as the job of the modeling framework (which calls service components or mediators when needed). Another part of this philosophy (more of a design decision) is that model components should not need to be grouped into "types" (e.g. based on the physical process they model, such as "infiltration"). All matching should be based on what each model needs from others or can provide to others.

• Many of the possible model attributes will be "provided" by most or all of the models in a "component set". For example, "model__time_step" would typically be listed as an output variable for every model in a component set. This means that model attribute names cannot be used to automatically match users to providers. For this to be possible, models would need to be grouped into named "types", model developers would need to be aware of these types, and the type name (e.g. perhaps a process name like "infiltration") would need to be inserted before the word "model" in model output variable names. While individual component models therefore have no way to ask for model attributes from another model in the component set, the framework "sees everything" and can keep track of which component it retrieved a model attribute from. For example, the service component that performs time interpolation for the models in a component set needs to know the individual time steps of each model in the set. (But actually gets this directly from the BMI "get_time_step()" function instead of using a "get_values()" call for the variable called "model__time_step".)

Attributes of Molecules

  quantity = attribute
  quantity = "bond_angle"
  quantity = "bond_dissociation_energy"
  quantity = "bond_energy"
  quantity = "bond_length"
  quantity = "proton_number" (total number of protons)
  quantity = "torsion_angle"
  quantity = "vibration_frequency"

Examples

water_molecule__actual_bond_angle
water_molecule__ideal_bond_angle  (or replace "ideal" by "VSEPR" ?)
water_molecule__hydrogen_number  (??? number of hydrogen atoms)
water_molecule_h_o__bond_dissociation_energy
water_molecule_h_o__bond_length
water_molecule_h_o_h__bond_angle

• A molecule is an electrically neutral group of two or more atoms held together by covalent chemical bonds.

• CSDMS Standard Names allow using the standard symbol for atoms of a particular element that occur in a molecule (but in lower case).

• There is distinction between "bond energy" and "bond dissociation energy".

• It seems that the bond energy, bond dissociation energy and bond length all depend on the molecule that the atoms are in and not just which two types of atoms are involved. If this is the case, then names should use the Part-of-another-Object Pattern (and perhaps the Object-to-object Quantity Pattern for the atoms), as in: "water_molecule_h_o_bond_length" and "water_molecule_h_o_bond_dissociation_energy".

• See: bond length, bond-dissociation energy and bond energy.

• Bond angles and lengths in molecules are defined as time averages.

• A bond_angle can be defined for 2 consecutive bonds and 3 atoms, as in "water_molecule_bond_angle" or "water_molecule_h_o_h_bond_angle". For a molecule in which all bond angles are the same, like benzene, we could have "benzene_c_c_c_bond_angle" or "benzene_c_c_h_bond_angle". See: Benzene.

• A torsion_angle can be defined for 3 consecutive bonds and 4 atoms, as in "ethane_h_c_c_h_torsion_angle". A synonym is "dihedral_angle".

• For ligands, a ligand cone angle and ligand bite angle can be defined.

• Valence shell electron pair repulsion theory (VSEPR) is a model in chemistry used to predict the shapes of molecules, such as "ideal bond angles".

• Molecules have "vibration frequencies" associated with all the different ways in which the atoms in the molecule can undergo a periodic motion relative to one another. (These relative positions don't change when the molecule rotates or translates as a whole.) See: Molecular vibration. (Individual atoms don't have vibration frequencies but they do have "emission frequencies".) In the so-called: rocking, scissoring, twisting and wagging vibrations, the bond lengths between atoms don't change. In stretching vibrations (symmetric or antisymmetric), the bond lengths change. For the CSDMS standard names we may be able to use names such as "ethylene_wagging_vibration_frequency".

• We could use "hydrogen_number" to quantify the number of hydrogen atoms in a molecule, but that term is also used in a medical context to mean the quantity of hydrogen that 1 gram of fat will absorb.

Attributes of Planets

  quantity = attribute   object = earth_asthenosphere
  object = earth_axis
  object = earth_core
  object = earth_core-mantle_boundary (known in geophysics as "cmb")
  object = earth_crust (move to planet attributes ??)
  object = earth_crust-mantle_boundary (known in geophysics as "moho", for Mohorovicic discontinuity, about 50 km depth)
  object = earth_ellipsoid
  object = earth_inner-core (solid iron core)
  object = earth_lithosphere
  object = earth_lithosphere-asthenosphere_boundary (known in geophysics as "lab")
  object = earth_lower-mantle
  object = earth_mantle
  object = earth_mantle_plume
  object = earth_orbit
  object = earth_outer-core (liquid iron core)
  object = earth_surface
  object = earth_transition-zone
  object = earth_upper-mantle

  Examples

earth_axis__tilt_angle     (see "Object vs. Adjective Rule")
earth_core-mantle_boundary__depth
earth_crust-mantle_boundary__depth
earth_ellipsoid__equatorial_radius
earth_ellipsoid__flattening_ratio
earth_ellipsoid__polar_radius
earth_inner-core_radius
earth_lithosphere-asthenosphere_boundary__depth
earth__mass
earth_orbit__eccentricity        (see "Object vs. Adjective Rule")
earth_outer-core__radius
earth__rotation_rate
earth__rotation_period      (see "Process_name + Quantity Pattern")
earth__sidereal_day
earth__solar_irradiation_constant    ( or just "solar constant"?  See notes.)
earth__standard_gravity_constant    (see the Constant template)

mars__mean_diameter
mars__solar_irradiation_constant
mars__standard_gravity_constant
mars_axis__tilt_angle
mars_ellipsoid__equatorial_radius

mercury_axis__precession_period
mercury_axis__precession_rate

venus_axis__tilt_angle
venus_orbit__aphelion_distance
venus_orbit__perihelion_distance
venus_orbit-ecliptic__inclination_angle  (or "venus_orbit_to_ecliptic" ?)
venus__solar_irradiation_constant
venus__standard_gravity_constant  (8.83 m s-2)

• Some of these are needed for proper georeferencing or modeling solar radiation via celestial mechanics.

• Notice that the word "ellipsoid" was inserted in three examples above. This is an example of the Object_name + Model_name pattern that is explained at the top of the document: CSDMS Object Templates.

• Solid earth geophysicists use the following acronyms/abbreviations: CMB = core-mantle boundary, LAB = lithosphere-asthenosphere boundary and "moho" = crust-mantle boundary, also called the Mohorovicic discontinuity, at about 50 km depth.

• See: Orbital elements for a discussion of the 6 parameters (including "inclination angle") that uniquely specify a specific orbit in astronomy.

• Note that Insolation refers to the solar irradiance measured at a given location on Earth, typically around 1000 W/m^2. The Solar irradiation constant is measured at the outer surface of Earth's atmosphere and is roughly 1366 W/m^2. Due to scattering and absorption in the atmosphere, the "insolation" is less than the "solar irradiation constant".

• See: Axial precession, Axial tilt, Declination, Ecliptic, Nutation, Position of the Sun, Precession, Right ascension, Solar azimuth angle, Solar elevation angle and Zenith.

Attributes of Processes

• See the template for Process Attributes.

Attributes of Products of a Company

  quantity = attribute

• See the CSDMS Object Template for "Product of a Company".

Attributes of Projectiles

  quantity = attribute
  object = projectile
  object = projectile_cross-section
  object = projectile_firing-site
  object = projectile_firing-site_land_surface
  object = projectile_firing-site_wind
  object = projectile_impact-crater
  object = projectile_rotation-axis
  object = projectile_target
  object = projectile_target_land_surface
  object = projectile_trajectory

  Examples

projectile__acceleration  (a vector)
projectile__altitude   (distance above the ground.  preferable to projectile_height)
projectile__angular_momentum
projectile__angular_velocity  (a vector)
projectile__azimuth_angle_of_impact_velocity
projectile__azimuth_angle_of_initial_velocity   (or of_firing_velocity ??)
projectile__azimuth_angle_of_velocity
projectile__diameter     (if spherical)
projectile__drag_coefficient
projectile__drag_force   (a vector)
projectile__firing_speed
projectile__firing_time
projectile__flight_duration
projectile__impact_depth
projectile__impact_force
projectile__impact_time
projectile__impact_velocity   (a vector)
projectile__initial_altitude      (this would be zero if fired from the ground or nonzero if fired from aloft)
projectile__initial_angular_momentum
projectile__initial_elevation    (this would be undefined if fired from aloft)
projectile__initial_latitude
projectile__initial_longitude
projectile__initial_velocity   (a vector)
projectile__kinetic_energy
projectile__length    (if cylindrical)
projectile__lift_coefficient
projectile__lift_force  (a vector)
projectile__mach_number
projectile__magnitude_of_drag_force
projectile__magnitude_of_lift_force
projectile__mass
projectile__mass-per-volume_density   #####
projectile__max_of_altitude    (highest point on the trajectory)
projectile__momentum
projectile__potential_energy
projectile__potential_range_distance   (max possible, if fired at 45 degree angle)
projectile__propelling_force
projectile__range_distance   (i.e. horizontal travel distance)
projectile__reynolds_number
projectile__roll_rotation_rate     #####
projectile__specific_kinetic_energy  [J kg-1]
projectile__specific_potential_energy [J kg-1]
projectile__speed
projectile__velocity    (a vector)
projectile__weight
projectile__x_component_of_acceleration
projectile__x_component_of_velocity
projectile__y_component_of_acceleration
projectile__y_component_of_velocity
projectile__z_component_of_acceleration
projectile__z_component_of_velocity
projectile__zenith_angle_of_impact_velocity     (also called "impact angle" or "terminal angle")
projectile__zenith_angle_of_initial_velocity    (also called "elevation angle", "launch angle" or "firing angle")
projectile__zenith_angle_of_velocity
  
projectile_cross-section__area
 
projectile_firing-site__elevation
projectile_firing-site__latitude
projectile_firing-site__longitude
projectile_firing-site__speed
projectile_firing-site__velocity  (a vector)
projectile_firing-site__x_component_of_acceleration
projectile_firing-site__x_component_of_velocity
projectile_firing-site__y_component_of_acceleration
projectile_firing-site__y_component_of_velocity
projectile_firing-site__z_component_of_acceleration
projectile_firing-site__z_component_of_velocity
 
projectile_firing-site_land_surface__aspect_angle
projectile_firing-site_land_surface__slope
projectile_firing-site_land_surface__slope_angle
 
projectile_firing-site_wind__azimuth_angle_of_velocity
projectile_firing-site_wind__speed
projectile_firing-site_wind__velocity  (a vector)
projectile_firing-site_wind__x_component_of_velocity
projectile_firing-site_wind__y_component_of_velocity
projectile_firing-site_wind__z_component_of_velocity
projectile_firing-site_wind__zenith_angle_of_velocity

projectile_impact-crater__depth         (insert "land_surface"  ??)
projectile_impact-crater__diameter
 
projectile_target__elevation
projectile_target__latitude
projectile_target__longitude
projectile_target__speed
projectile_target__velocity  (a vector) 
projectile_target__x_component_of_acceleration
projectile_target__x_component_of_velocity
projectile_target__y_component_of_acceleration
projectile_target__y_component_of_velocity
projectile_target__z_component_of_acceleration
projectile_target__z_component_of_velocity
  
projectile_target_land_surface__aspect_angle
projectile_target_land_surface__slope
projectile_target_land_surface__slope_angle
 
projectile_trajectory__curvature
projectile_trajectory__length

• "Projectile" is a generic object name that could refer to a cannonball, bullet, arrow, crossbow bolt, spear, missile, etc. We may want to make a distinction between projectiles (that are fired or launched) and meteors (that "just arrive").

• We could use "initial_elevation", "initial_latitude" and "initial_longitude" as quantity names with "projectile" as the object. However, using "projectile_firing-site" as the object name would make it possible to specify additional attributes (other than elevation, latitude and longitude) of the firing site, such as the topographic slope or aspect. It is also possible for the "firing site" to be moving (e.g. aircraft or ship), and then we need to be able to specify its velocity as well.

• Roll_angle, pitch_angle and yaw_angle are used for aircraft and perhaps could be used to describe rotation of a projectile in flight.

• See: Drag coefficient, Euler angles, Impact depth, Lift coefficient, Mach number, Magnus effect, Projectile, Range of a projectile, Rifling, and Trajectory of a projectile.

Attributes of Radiation

  quantity = attribute
  quantity = "absorbance"
  quantity = "albedo"
  quantity = "amplitude"
  quantity = "emission_angle"
  quantity = "emissivity"
  quantity = "flux"
  quantity = "frequency"
  quantity = "incidence_angle"
  quantity = "intensity"
  quantity = "period"
  quantity = "reflectivity"
  quantity = "standard_refraction_index"
  quantity = "transmittance"
  quantity = "wavelength"

  Examples:

None yet.

• Albedo is also called "diffuse reflectivity" or "reflectance coefficient".

• See the Radiation template on this page for numerous examples of radiation fluxes.

• Note that "refraction_index" is an example of a quantity that really requires two objects to be specified, electromagnetic radiation or light of a particular wavelength and the medium that it is traveling through (e.g. air, water, vacuum). However, standard refractive index measurements (see List of refractive indices) are taken at the yellow doublet sodium D line, with a wavelength of 589 nanometers. So in CSDMS standard names the insertion of the adjective "standard" means that only one object, the medium, needs to be specified. So "air_standard_refraction_index" would be a valid and unambiguous name, but 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".) We may also want to allow names such as "550_nm_light_in_air_refraction_index".

• See: Absorbance, Albedo, Amplitude, Electromagnetic radiation, Frequency,Intensity in physics,Reflectivity, Refraction index, Transmittance, Visible radiation and Wavelength.

Attributes of Sea Ice

  quantity = attribute

  Examples

sea_ice__age
sea_ice__area
sea_ice__area_fraction   (vs. "sea_ice_concentration"; see Concentration)
sea_ice__emissivity
sea_ice__extent
sea_ice__thickness
sea_ice__volume

• What about "sea_ice_mass_balance" ? The term "mass_balance" is also used in glaciology but is confusing outside of that domain.

• The quantity "sea_ice_extent" is related to "sea_ice_area" but involves a "reference threshold" (as a percentage, usually 15%) that must be specified with an <assume> tag in a Model Metadata File. See Measurement of sea ice. Also see Reference Quantities.

• See Concentration, Fraction and Thickness.

Attributes of Soil

  quantity = attribute

  Examples

land_surface_water__depth
land_surface_water__infiltration_rate
 
model_soil_layer_0__porosity
model_soil_layer_0__thickness
model_soil_layer_0__wetted_thickness

soil_active_zone__thickness
soil_air__volume_fraction    (not same as porosity)
soil__brooks_corey_b_parameter   (lambda = 1/b)
soil__brooks_corey_eta_parameter
soil__brooks_corey_lambda_parameter
soil__brooks_corey_smith_c_parameter
soil__brooks_corey_smith_pressure_head_offset   #####
soil_clay__volume_fraction
soil__freeze_depth  ###
soil_frozen_water__volume_fraction
soil__green_ampt_capillary_length   (denoted as G, or "length_scale" ??)
 ## (or "green_ampt_g_parameter")
soil_layer__thickness
soil_loam__volume_fraction
soil__mass_density
soil__porosity
soil__reference_depth_temperature
soil_sand__volume_fraction
soil_silt__volume_fraction
soil__smith_parlange_gamma_parameter
soil__specific_permeability   (function of medium only, not fluid)
soil_surface_water__baseflow_emergence_rate   (nonstandard, but unambiguous)
soil_surface_water__volume_fraction  (water content)
soil_surface_water__infiltration_rate
soil_surface_water__ponding_time 
soil_surface_water__time_integral_of_infiltration_rate
soil__temperature
soil__temperature_reference_depth
soil__thaw_depth  ###
soil__thermal_capacity
soil__thermal_conductivity
soil__thickness
soil_water__air_dried_pressure_head
soil_water__bubbling_pressure_head   (or air_entry_pressure_head  ??)
soil_water__diffusivity
soil_water__effective_hydraulic_conductivity
soil_water__effective_saturated_hydraulic_conductivity
soil_water__effective_saturation     (same as "normalized_volume_fraction")
soil_water__field_capacity_pressure_head
soil_water__field_capacity_volume_fraction  (water content)
soil_water__hydraulic_conductivity    (function of medium and fluid)
soil_water__hygroscopic_pressure_head
soil_water__hygroscopic_volume_fraction   (water content)
soil_water__infiltrability  (fc, "potential_infiltration_rate"  ??)
soil_water__initial_volume_fraction       (water content)
soil_water__normalized_hydraulic_conductivity
soil_water__normalized_volume_fraction    (water content)
soil_water__oven_dried_pressure_head
soil_water__potential_infiltration_rate   (less standard term for fc = infiltrability)
soil_water__pressure_head
soil_water__relative_hydraulic_conductivity   (K/Ks)
soil_water__residual_volume_fraction      (water content)
soil_water__saturated_hydraulic_conductivity   (function of medium and fluid)
soil_water__saturated_volume_fraction
soil_water__sorptivity      ##### check
soil_water_table__depth
soil_water_table__recharge_rate   ####
soil_water__volume_fraction
soil_water_wetting_front__depth   #####
soil_water__wilting_point_pressure_head
soil_water__wilting_point_volume_fraction
soil_water__x_component_of_darcy_velocity    (darcy_velocity = specific_discharge, macroscopic = volume flux)
soil_water__y_component_of_darcy_velocity
soil_water__z_component_of_darcy_velocity
soil__van_genuchten_alpha_parameter
soil__van_genuchten_m_parameter
soil__van_genuchten_n_parameter
soil__void_ratio   (not same as porosity)

• The quantity name darcy_velocity is used for the volume flux that is otherwise known as the specific discharge. Freeze and Cherry (1979) mention both names, but emphasize the latter in order to make a clear distinction between it and the microscopic fluid velocity within pores. It has units of velocity and in the general case is modeled as a (macroscopic) three-dimensional velocity field (i.e. 3 components). Retaining the adjective "darcy" serves as a reminder of its origins and macroscopic nature.

• The quantity name volume_fraction is used instead of the more standard term water content. By keeping the word "water" in the (compound) object name "soil_water" and out of the quantity name, we maintain consistency with other standard names. "Volume_fraction" is also more self-explanatory.

• The quantity name potential_infiltration_rate is used instead of the alternate name infiltrability since it is the max possible infiltration rate.

• The quantity name baseflow_emergence_rate is used instead of "baseflow_seepage_rate" since the word seepage leaves ambiguity as to whether the flow is into the surface or out of the surface.

Attributes of Topography

  quantity = attribute
  quantity = "aspect_angle" (aspect is not used by itself)
  quantity = "elevation"
  quantity = "laplacian_curvature"
  quantity = "mean_curvature"
  quantity = "plan_curvature"
  quantity = "profile_curvature"
  quantity = "slope" [unitless = rise/run = L/L]
  quantity = "slope_angle" [radians or degrees]
  quantity = "specific_contributing_area"
  quantity = "streamline_curvature"
  quantity = "tangential_curvature"
  quantity = "total_contributing_area"

  Examples

bedrock_surface__elevation
bedrock__uplift_rate
domain_boundary__lowering_rate
glacier_surface__elevation
glacier_surface__slope
ground_water_table_surface__aspect_angle

land_surface__aspect_angle   # (angle of reverse gradient vector)
land_surface__elevation
land_surface__elevation_increment
land_surface__initial_elevation
land_surface__laplacian_curvature
land_surface__latitude
land_surface__longitude
land_surface__max_of_elevation
land_surface__max_of_elevation_increment
land_surface__mean_curvature
land_surface__min_of_elevation
land_surface__min_of_elevation_increment
land_surface__plan_curvature
land_surface__profile_curvature
land_surface__slope
land_surface__slope_angle
land_surface__specific_contributing_area   (measured by D8, D-inf, etc.)
land_surface__streamline_curvature
land_surface__tangential_curvature
land_surface__time_derivative_of_elevation
land_surface__total_contributing_area  (measured by D8, D-inf., etc.)
land_surface__x_component_of_gradient_of_elevation
land_surface__y_component_of_gradient_of_elevation
land_surface__x_component_of_gradient_of_slope
land_surface__y_component_of_gradient_of_slope
land_surface__x_derivative_of_elevation
land_surface__y_derivative_of_elevation
 
sea_water_surface__elevation
sea_water_surface__mean_curvature
sea_water_surface__slope

• Note that many of these quantities are defined in terms of first or second derivatives, which requires a certain degree of smoothness (differentiable or twice differentiable). Real topography is generally not this smooth, especially at small scales, but these quantities are nevertheless useful and can be computed from DEMs. In the CSDMS Standard Names, the Object_name + Model_name Pattern indicates that the word "surface" should be inserted in front of the quantity name when the quantity is only defined for some kind of idealized "model" surface. See the Surface template.

• "Specific contributing area" (SCA) is a quantity that can be defined for each point on a mathematical surface as the (upstream) contributing area per unit contour length. "Total contributing area" (TCA) is a quantity obtained from integrating SCA over a line segment, such as the width of a grid cell projected in the direction of the surface gradient. The relationship between TCA and SCA is similar to that between water discharge (Q) and unit-width water discharge (q).

• "contour curvature" is a synonym for "plan curvature". "streamline curvature" is not well-known. See: Peckham (2011).

• See: Aspect, Bathymetry, Curvature, Drainage basin, Elevation, Geomorphometry, Slope and Topography.

• There is an international society called: geomorphometry.org that meets every two years.

Attributes of a Water Tank

  quantity = attribute

  Examples

atmosphere_water__precipitation_duration
atmosphere_water__liquid-equivalent_precipitation_rate
tank_horizontal-cross-section__area
tank_horizontal-cross-section__radius
tank_outlet_cross-section__area
tank_outlet_water__flow_speed
tank_water__depth
tank_water__initial_depth
tank_water__volume

• One of the BMI examples is for a simple model of a cylindrical water tank with an open top that can receive rainfall and a smaller outlet that the water drains from.

• A word like "rainwater_tank", "storage_tank" or "rain_barrel" might be better than "tank", which has alternate meanings.

Capacity

  base_quantity = "capacity"
  base_quantity = "carrying_capacity"
  base_quantity = "thermal_capacity"

  Examples

air__thermal_capacity
aluminum__specific_thermal_capacity
earth_human__carrying_capacity    (need to specify two objects ??)
iron__thermal_capacity
snow__thermal_capacity
soil__thermal_capacity

• The more general quantity "thermal_capacity" is used instead of "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 thermal capacity (how well they retain heat). See: Cookware and bakeware.

• The term "carrying_capacity" follows the Process_name + Quantity Pattern and is the maximum population size for a given ecosystem. See: Carrying capacity.

• Other quantities that contain "capacity" are: battery capacity, channel capacity and combining capacity.

• 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 CSDMS Object Templates page for more information.

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: Electric charge and Elementary charge.

Circulation

  base_quantity = "circulation"

  Examples airfoil_enclosing-curve__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: Circulation.

Code

  base_quantity = "code"

  Examples

location__postal_code     (See: Postal code.)
watershed__pfafstetter_code
watershed__usgs_hydrologic_unit_code

• For hydrologic features such as rivers, unique identification numbers such as the USGS Hydrologic Unit Code (or "HUC number") and Pfafstetter Code are used.

• Codes sometimes include both numbers and letters.

• See Number.

Coefficient

  base_quantity = "coefficient"

  Examples

airfoil__drag_coefficient
airfoil__lift_coefficient
atmosphere__beer_lambert_attenuation_coefficient
iron__thermal_expansion_coefficient
channel_bed__manning_coefficient
glacier__glen_law_coefficient
math__binomial_coefficient     (See Constants in Math)
polynomial__leading_coefficient
rubber_on_concrete__kinetic_friction_coefficient
rubber_on_pavement__static_friction_coefficient
salt_in_water__diffusion_coefficient   ####
steel_spring__hooke_law_coefficient    [kg s-2]    (the "spring constant" in Hooke's law)
watershed__flint_law_coefficient
watershed__hack_law_coefficient

• Note that some of these use the Object-in-object Quantity Pattern and many others use the Process_name + Quantity Pattern (e.g. "expansion_coefficient").

• Coefficients often occur in empirical laws, usually as a multiplicative factor to one of the other variables in an equation.

• A "bulk exchange coefficient" for water vapor or heat (e.g. in the atmosphere) is sometimes used. This appears to be a synonym for "transfer coefficient", which can be applied to mass, momentum or heat transfer. See: Heat transfer coefficient and Mass transfer coefficient. It is essentially a diffusion coefficient that is associated with the interface between a fluid and a solid/boundary or between two fluids. Transfer coefficients are associated with boundary layers in fluids and are sometimes computed using the logarithmic law of the wall. The adjectives "bulk" and "overall" are frequently added, as in "overall heat transfer coefficient". A mass transfer coefficient has SI units of [m s-1] while a heat transfer coefficient has SI units of [W m-2 K-1].

• 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 "drag coefficient". Ch is also called the Stanton number.

• "Manning's coefficient" is sometimes called "Manning's roughness coefficient" or "Manning's roughness parameter" or something similar. The word "roughness" is not needed to remove ambiguity, however. Manning's n is still usually referred to as a coefficient even though it appears in the denominator (i.e. its inverse is the multiplicative factor).

• 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 emitted to incident radiation, I(x)/I(0), a positive number less than 1. See: Absorbance, Air mass,Attenuation coefficient,Beer-Lambert Law, Optical depth and Transmittance.

• See: Attenuation coefficient, Ballistic coefficient, Binomial coefficient, Coefficient, Drag coefficient, Friction, Heat transfer coefficient, Lift coefficient, Manning formula, Mass diffusivity, Mass transfer coefficient, Partition coefficient, Reflection coefficient, Skin friction coefficient, Thermal expansion and Transmission coefficient.

• See Constant, Exponent, Factor, Index, Number and Parameter.

• See Friction.

Component

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

  Examples

atmosphere__east_component_of_flow_velocity
atmosphere__north_component_of_flow_vorticity
channel_water__x_component_of_flow_velocity
sea_water__down_east_component_of_flow_shear_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 "flow_velocity" is used for fluid flows instead of just "velocity". This also applies to "flow_vorticity" and "flow_shear_stress".

• See Stress, Velocity and Vorticity.

• This was changed from a "quantity suffix" to a vector operation on 2/7/13. See CSDMS Operation Templates.

Concentration

  base_quantity = "concentration"
  quantity = "mass_concentration" [kg m-3]
  quantity = "molar_concentration" [mol m-3] (molarity)
  quantity = "number_concentration" [m-3]
  quantity = "volume_concentration" [1] = [m3 / m3]

  Examples

channel_water_suspended_sediment__mass_concentration
magnesium_chloride_in_sea_water__molar_concentration
sea_water_suspended_sediment__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: Mixing ratio.

• "Molar concentration" is also called "molarity". See: Molarity.

• "Volume concentration" is also called "volume fraction". See Fraction.

• The term "osmotic concentration" is also used.

• See: "Mineral makeup of seawater".

• See: Concentration, Seawater and Sediment transport.

Conductivity

  base_quantity = "conductivity"
  quantity = "electrical_conductivity" [siemens m-1] or [ohm-1 m-1]
  quantity = "hydraulic_conductivity" [m s-1]
  quantity = "ionic_conductivity"
  quantity = "thermal_conductivity" [W m-1 K-1]

  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 CSDMS Assumption Names for more information.

• "Relative hydraulic conductivity" is the ratio of (K / K_sat). See Smith (2002).

• See: Electrical conductivity, Hydraulic conductivity,Ionic conductivity and Thermal conductivity.

Constants in Math

  base_quantity = "constant"
  quantity = "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 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 golden ratio.

• See the Dimensionless Number template.

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__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__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]
physics__planck_mass_constant    [kg]  (about 2.17651e-8)
physics__reduced_planck_constant
physics__rydberg_constant            [m-1]
physics__static_relative_permittivity
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_light_speed_constant        [m s-1]
physics__vacuum_electric_permittivity_constant   [F/m]  ("electric constant")
physics__vacuum_magnetic_permeability_constant  [N A-2] or [H m-1]   ("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. Or we could remove the object name requirement when the base quantity is "constant".

• 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__fusion_specific_latent_heat          (334 [kJ kg-1])
 water__vaporization_specific_latent_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 Latent heat.

• The modern name for "Avogadro's number" is the "avogadro_constant". (See 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: Standard gravity and Gravity of Earth.

• While the coefficient in Hooke's law is often called the spring constant, we instead use 'steel_spring__hooke_law_coefficient for consistency with coefficients in other empirical laws.

• See: Boltzmann constant,Coulomb constant, Elementary charge, Fine-structure constant,Gravitational coupling constant, Ideal gas constant,Planck constant,Psychrometric constant,Rydberg constant,Stefan-Boltzmann constant, Universal gravitational constant, Vacuum electric permittivity, Vacuum magnetic permeability and von Karman constant.

• See: Physical constant.

Content

  base_quantity = "content"
  quantity = "energy_content"
  quantity = "mass_content"
  quantity = "water_content"

  Examples

coal__thermal_energy_content
dry_wood__thermal_energy_content
gas__thermal_energy_content
 
soil__field_capacity_water_content
soil__hygroscopic_water_content
soil__initial_water_content
soil__normalized_water_content  (also called "effective saturation")
soil__residual_water_content
soil__saturated_water_content
soil__wilting_point_water_content
 
snow__cold_content  ? (must be overcome before melting starts to occur)
snow__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. While "soil_water_content" is a fairly standard term in hydrology, it would be perfectly valid and perhaps more clear to use the term "water_in_soil_volume_fraction".

• The quantity "thermal_energy_content" can be applied to substances like air and snow but is often used in the context of fuels like coal, gas and wood.

• In CF Standard Names, "content" indicates a quantity per unit area. However, in infiltration theory, "soil_water_content" is a "volume_fraction". CF has "soil_moisture_content", "soil_moisture_content_at_field_capacity" and "soil_carbon_content". See Water Content.

• Do we want to distinguish between: gravimetric_water_content and volumetric_water_content ?

• Many CF Convention 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.

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)
 
eastward_coordinate  (for a model; if not same as longitude)
westward_coordinate
northward_coordinate (for a model;  if not same as latitude)
southward_coordinate

r_coordinate    (Cylindrical and Spherical coordinates, with azimuth_angle and zenith_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: Geographic coordinates.

• For spherical coordinates, we would usually use "azimuth_angle" and "zenith_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: Barycentric coordinates (astronomy), Barycentric coordinates (for a triangle or other simplex), Canonical coordinates, Coordinate system, Fermi coordinates, Fractional coordinates (crystallography), Galilean transformation, Generalized coordinates, Isothermal coordinates, Normal coordinates (from differential geometry) and 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.

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".

Count

  base_quantity = "count"
  quantity = "blood_" + [cell type] + "_cell_count"

  Examples

channel_bed__wolman_pebble_count
human_blood_platelet__count
human_blood_red-cell__count
human_blood_white-cell__count

• This quantity name is sometimes used when the attribute being quantified can only take integer values, as in the examples above.

• In the case of blood cell counts, the units are usually a number per volume (e.g. number per microliter). See: Blood cell count. Should the quantity name then be: "unit_volume_count", or perhaps should "unit_volume" be added to the end of the object name? Is a platelet technically considered to be a type of blood cell?

• The "Wolman pebble count" due to M. Gordon "Reds" Wolman is sometimes used in river hydraulics and sediment transport.

• 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 Count data and the Number template.

Curvature

• See the Attributes of Topography template which lists several types of curvature. However, curvature can also be defined for curves, such as coastline curves and space curves (or trajectories).

Density

  base_quantity = "density"

  Examples

air__density
air__stp_density   (stp = standard temperature and pressure)
friedmann_universe__critical_density
sea_water__density
watershed__drainage_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). To avoid ambiguity, perhaps standard names like mass-per-volume_density, mass-per-area_density, energy-per-area_density, number-per-area_density, "number-per-volume_density", length-per-area_density, charge-per-area_density, "bits-per-area_density" and "torque-per-volume_density" should be used to remove any ambiguity. Similar issues occur for Concentration (see section by that name). Also see the section for Flux.

• Maybe expand this to "mass_density" to avoid any ambiguity. Units for "mass_density" would always be [kg m-3]. Consider cases like: "drainage_density" [L-1]

• The adjective "bulk" is often inserted before density.

• Physicists sometimes use the term "flux_density".

• Hydrologists use the term "drainage_density", which is defined as the total length of channels in a watershed divided by the watershed area. Similarly, "source_density" refers to the total number of sources (i.e. channel heads) in a watershed divided by the watershed area.

• Other valid quantities include "current_density", "electron_density" (in plasma physics), "thermal_energy_density" and "magnetic_energy_density".

• See: Area density, Critical density,Current density, Density, Drainage density, Electron density, Energy density, Knot density, Linear density, Memory storage density, Number density, Orthobaric density, Particle density, Population density, Potential density, Power density, Probability density function, Relative density,Surface power density, Torque density and Vapour density.

Depth

  base_quantity = "depth"
  quantity = "precipitable_depth"
  quantity = "secchi_depth"

  Examples

atmosphere_vertical-column_water-vapor__precipitable_depth
channel_water__mean_depth  ??
ground_water_table__depth    ### (underground or subsurface vs. ground ?)
sea_water__depth  (or sea_floor_depth ?? #######)
sea_water__secchi_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: Secchi disk.

• While the term "precipitable_water_content" is commonly used, its units of length are not really consistent with the base quantity "content". However, the terms "precipitable water depth" and "precipitable depth of water vapor" are also used and imply units of length. An unambiguous standard name for this quantity might be: "water_vapor_in_vertical_air_column__precipitable_depth", which uses the Object-in-object Quantity Pattern.

• See Altitude, Elevation, Height and Thickness.

Diameter

  base_quantity = "diameter"

  Examples

bluejack_oak_tree_trunk__diameter
crater_circle__diameter      (see Object_name + model_name Pattern)
rooted_tree_graph__diameter
square__diameter
watershed__diameter

• This quantity usually has units of length (except for rooted tree graphs).

• Although often associated with a circle, the general definition of 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 convex hull. In graph theory, the diameter of a rooted 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.

Diffusivity

  base_quantity = "diffusivity"
  quantity = "magnetic_diffusivity" [m2 s-1]
  quantity = "mass_diffusivity" [m2 s-1]
  quantity = "momentum_diffusivity" [m2 s-1] (nickname for kinematic_viscosity)
  quantity = "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: Eddy diffusion.

• See: Magnetic diffusivity,Mass diffusivity,Kinematic viscosity, Momentum diffusion, Thermal diffusivity and Thermal conduction.

Dimension

  base_quantity = "dimension"
  quantity = "box_counting_dimension"
  quantity = "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: Box-counting dimension, Dimension, Fractal dimension, Hausdorff dimension and Packing dimension.

Dimensionless Numbers

  quantity = [ famous person's name ] + "_number"

  Examples

air_helium-plume__richardson_number
airplane__mach_number
channel_water__reynolds_number
channel_water__froude_number
heat_equation__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 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 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.

Discharge or Volume Flow Rate

  quantity = "volume_flow_rate"
  quantity = "volume-per-unit-contour-length_flow_rate" (or per-unit-length ??)
  quantity = "incoming_volume_flow_rate"
  quantity = "outgoing_volume_flow_rate"

  Examples

channel_water__volume_flow_rate [m3 s-1]
lake_water__incoming_volume_flow_rate [m3 s-1]
lake_water__outgoing_volume_flow_rate [m3 s-1]
watershed_outlet_water__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]. Here we use "volume-per-unit-length_flow_rate" instead. Note that this may also be used for the "lateral inflow rate" to the sides of a channel as in: "channel_bank_water__volume-per-length_flow_rate".

• See: Discharge,Volumetric flow rate, Volumetric flux and 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 "water_suspended-sediment__mass_flow_rate" instead of "water_suspended-sediment__discharge", since discharge has units of [volume / time].

• See the Flow Rate template.

Distance

  base_quantity = "distance"

  Examples

channel_centerline_end_to_end__straight_distance    #####
earth_to_sun__mean_distance
particle_to_sea_floor__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 Hamming distance measures the dissimilarity of two text strings. See: Metric, Distance, Euclidean distance, Uniform norm and Taxicab geometry (or "Manhattan distance").

Duration

  base_quantity = "duration"
  quantity = [process name] + "_duration" (e.g. exposure_duration, precipitation_duration)

  Examples

aircraft__flight_duration
atmosphere_water__precipitation_duration  (vs. "rainfall duration")
earth_mean-solar-day__duration
earth_sidereal-day__duration
earth_stellar-day__duration
earth__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 CSDMS Process Names for a list of process names.

Efficiency

  base_quantity = "efficiency"
  quantity = "electrical_efficiency"
  quantity = "luminous_efficiency"
  quantity = "mechanical_efficiency"
  quantity = "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: Carnot heat engine, Electrical efficiency, Energy conversion efficiency, Fuel efficiency, Luminous efficiency, Mechanical advantage, Mechanical efficiency and Thermal efficiency.

Elevation

  base_quantity = "elevation"

  Examples

bedrock_surface__elevation
ground_water-table_surface__elevation
land_surface__elevation
sea_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.

Energy

  base_quantity = "energy"
  quantity = "electric_energy"
  quantity = "free_energy"
  quantity = "internal_energy"
  quantity = "kinetic_energy"
  quantity = "potential_energy"
  quantity = "specific_energy"
  quantity = "thermal_energy"

  Examples

ball__potential_energy
turbulence__kinetic_energy
water__gibbs_free_energy

• The SI unit for energy is Joules.

• Specific energy is energy per unit volume or mass.

• Some possible forms of energy are thermal, chemical, radiant, nuclear, magnetic, elastic sound, mechanical, luminous and mass. See Energy.

• See Gibbs free energy, Helmholtz free energy and Thermodynamic free energy.

Exponent

  base_quantity = "exponent"

  Examples

channel_water_suspended-sediment__volume_flow_rate_law_area_exponent
channel_water_suspended-sediment__volume_flow_rate_law_coefficient
glacier__glen_law_coefficient
glacier__glen_law_exponent
watershed__flint_law_coefficient
watershed__flint_law_exponent
watershed__hack_law_coefficient
watershed__hack_law_exponent

• Exponents often occur in empirical laws.

• Systems that can undergo phase transitions are often characterized by a critical exponent.

• See Coefficient, Constant, Factor, Index, Number and Parameter.

Factor

  base_quantity = "factor"

  Examples

particle__cunningham_correction_factor
oscillator__q_factor
pipe_water__darcy_friction_factor  (same as moody_friction_factor)
pipe_water__fanning_friction_factor
sine_wave__crest_factor
sun__protection_factor

• Use "manning_coefficient" instead of "manning_friction_factor".

• Many different types of Shape factor are used in image analysis, such as the "circularity_shape_factor", "elongation_shape_factor", "compactness_shape_factor" and "waviness_shape_factor".

• A model may use an "adjustment_factor", "correction_factor" or "compensation_factor".

• See: Atomic form factor (or atomic scattering factor), Crest factor, Q factor, Sun Protection Factor (SPF) and View factor.

• See Coefficient, Constant, Exponent, Index, Number and Parameter.

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 Flag (computing).

Flow Rate

  base_quantity = "flow_rate"
  quantity = "mass_flow_rate"
  quantity = "momentum_flow_rate"
  quantity = "energy_flow_rate"
  quantity = "volume_flow_rate"
  quantity = "mole_flow_rate"

  Examples

channel_water__incoming_volume_flow_rate  (##### or channel_entrance__volume_flow_rate ???
channel_water_suspended-sediment__outgoing_mass_flow_rate
lake_water__incoming_volume_flow_rate
watershed_outlet_water__outgoing_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. In the CSDMS Standard Names, the quantity "discharge" is viewed as equivalent to "volume_outflow_rate".

• 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: Power.

• See: Discharge,Volumetric flow rate and Mass flow rate.

• See the templates for Discharge, Flux and Rate of a Process.

Flux

  base_quantity = "flux"
  quantity = "mass_flux"
  quantity = "momentum_flux"
  quantity = "energy_flux"
  quantity = "volume_flux"
  quantity = "mole_flux" (perhaps this should be "number_flux" to be independent of units.)
  quantity = process_name + "_flux"   (e.g. "radiation_flux")

  Examples

atmosphere__absorbed_incoming_shortwave_radiation_flux
land_surface__outgoing_longwave_radiation_flux       (emitted and upward)
land_surface__incoming_longwave_radiation_flux    (incident and downward)
sea_floor_surface__incoming_shortwave_radiation_flux
sea_surface__reflected_incoming_shortwave_radiation_flux 
sea_water__downward_incoming_shortwave_radiation_flux

• See the section on Radiation on the 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: Earth's radiation balance.

• A process name frequently precedes the base quantity "flux" in accordance with the Process_name + Quantity Pattern. Examples include "evaporation_flux", "radiation_flux", "precipitation_flux". Note that "precipitation_rate", "evaporation_rate", "infiltration_rate", "melt_rate" and "uplift_rate" are standard quantity names with units of [m s-1] and each is actually a volume flux.

• What about "luminous flux" (for visible light)? See: Luminous flux.

• See: Flux, 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 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.

Fraction

  quantity_suffix = "fraction"
  quantity = "area_fraction"
  quantity = "mass_fraction"
  quantity = "mole_fraction"
  quantity = "time_fraction"
  quantity = "volume_fraction"

  Examples

earth_surface_land_covered__area_fraction
earth_surface_water_covered__area_fraction
 # surface of a 3D region vs. mathematical surface
 
land_agricultural_portion__area_fraction
land_arable_portion__area_fraction
land_burned_portion__area_fraction
land_clouded_portion__area_fraction  # (cloud_covered ??)
land_farmed_portion__area_fraction
land_flooded_portion__area_fraction
land_flooded_portion_water__max_of_depth
land_forested_portion__area_fraction
land_glaciated_portion__area_fraction  # (ice_covered ??)
land_grazing_portion__area_fraction  #####
land_irrigated_portion__area_fraction
land_lake_covered_portion__area_fraction
land_water_covered_portion__area_fraction
land_privately_owned_portion__area_fraction
land_publicly_owned_portion__area_fraction
land_snow_covered_portion__area_fraction
land_urban_portion__area_fraction
land_vegetated_portion__area_fraction
land_wetland_covered_portion__area_fraction
watershed_forested_portion__area_fraction
 
rocket_payload__mass_fraction
rocket_propellant__mass_fraction  (See: Propellant mass fraction.)
 
soil_clay__volume_fraction   (using object_in_object pattern)
soil_sand__volume_fraction
soil_silt__volume_fraction

sea_water_oxygen__volume_fraction  (modified from CF name below)  
soil_frozen-water__volume_fraction   (modified from CF name below)

• 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.

• 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 the reserved word "vs" can be used in a construction like: "land_vs_water__area_fraction". Or should we just use: "dry_land__area_fraction"?

• 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 watershed, then constructions like: "watershed_forested-land__area_fraction" can be used and conform to the Part of Another Object Pattern.

• 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 "water_in_soil_volume_fraction" instead would be consistent with the Object-in-object Quantity Pattern.

Friction

• Friction is not a quantity and is really a force as opposed to a process. It is not included in this list of 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.)
manning_roughness_coefficient
mean_roughness_length   ("z0" for law of the wall)
shear_stress   (See the Stress template.)
static_friction_coefficient

• A Google search indicates that "friction_rate" is sometimes used in connection with air ducts.

Frequency

  base_quantity = "frequency" [1/second]
  quantity = "angular_frequency" [radians/second]

  Examples

cesium_atom__characteristic_emission_frequency
sea_water__brunt_vaisala_frequency   (also called "buoyancy_frequency")
sea_water_surface_wave__frequency

• Units of frequency are usually hertz = [1/second].

• For periodic waves, the frequency is equal to the phase velocity divided by the wavelength. See the Period and Wavelength templates.

• See Wikipedia: Brunt–Väisälä frequency.

• See Normalized frequency, Nyquist frequency.

Fuel Efficiency

  quantity = "fuel_consumption_rate" ["gallons per mile" or "liters per km"]
  quantity = "fuel_economy" ["miles per gallon" or "km per liter"]
  quantity = "fuel_specific_energy_content" [Joules / kg]

  Examples

automobile_fuel__consumption_rate
automobile_fuel__economy
gm_hummer_fuel__consumption_rate
toyota_corolla_fuel__economy

• 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: Fuel efficiency of vehicles and Efficient energy use.

Head

  base_quantity = "head"
  quantity = "friction_head"
  quantity = "hydraulic_head"
  quantity = "pressure_head"
  quantity = "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: Hydraulic head, Pressure head and Total hydraulic head.

Heat

  base_quantity = "heat"
  quantity = "latent_heat"
  quantity = "sensible_heat"

  Examples

water__fusion_specific_latent_heat          (334 [kJ kg-1])
water__vaporization_specific_latent_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: Heat, Latent heat, Sensible heat and Thermodynamic databases for pure substances.

• See Energy and Flux of Heat or Energy.

Height

  base_quantity = "height"
  quantity = "geopotential_height"
  quantity = "reference_height"

  Examples

empire-state-building__height
bluejack-oak-tree__mean_height
human__mean_height

• See Geopotential height, Geostrophic wind and Above mean sea level.

• See Reference Quantities.

Humidity and Relative Saturation

  base_quantity = "humidity"
  quantity = "absolute_humidity" (is "volumetric_humidity" a synonym ?)
  quantity = "relative_humidity"
  quantity = "relative_saturation"
  quantity = "specific_humidity"

  Examples

air_carbon-dioxide__relative_saturation   ## CHECK
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.

Increment

  operation_prefix = "increment_of"

  Examples

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.

Index

  base_quantity = "index"

  Examples

air__standard_refraction_index
consumer__price_index
ecosystem__diversity_index
model_grid_cell__column_index
model_grid_cell__row_index
__normalized_difference_vegetation_index
__palmer_drought_index

soil__moisture_index
watershed_soil__topgraphic_index
watershed_soil__wetness_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".

• 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.

• See Coefficient, Constant, Exponent, Factor, Number and Parameter.

• See: Forest fire weather index, Haines index, Heat index, Jaccard index, Lifted index, Normalized Difference Vegetation Index, Palmer drought index, Price index and Refraction index.

Latitude

  base_quantity = "latitude"

  Examples

model_grid_cell_center__latitude
model_grid_cell_north-edge__latitude
model_grid_cell_south-edge__latitude
model_grid_north-edge__latitude
model_grid_south-edge__latitude

• Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?

• Typical units are "decimal degrees".

• The adjective "geodetic" may be needed in some cases.

• This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Metadata File. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".

• See: Geodetic system, Geographic coordinate system, Geographical distance, Latitude, Longitude and Reference ellipsoid.

• See the section for Coordinates above.

Limit

  operation_prefix = "limit_of"

  Examples

human__lower_limit_of_hearing_frequency     (Note:  hearing is a process name)
human__upper_limit_of_hearing_frequency
neutron_star__tolman_oppenheimer_volkoff_limit_mass
human_eye_photon__lower_limit_of_detection_number   (process_name + quantity)
white_dwarf_star__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.

Longitude

  base_quantity = "longitude"

  Examples

model_grid_cell_center__longitude
model_grid_cell_east-edge__longitude
model_grid_cell_west-edge__longitude
model_grid_east-edge__longitude
model_grid_west-edge__longitude

• Should we use "geographic_grid" instead of just "grid" for the object name in the examples above?

• Since "center", "east-edge", "west-edge", 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 "east-edge" is a single object or sub-object.

• Typical units are "decimal degrees".

• The adjective "geodetic" may be needed in some cases.

• This quantity is always relative to a particular (reference) ellipsoid model which should be specified using an <ellipsoid> tag in the Model Metadata File. Similarly, <datum> and <projection> tags can be used. An <assume> tag should also be used to specify "geographic_coordinate_system".

• See: Geodetic system, Geographic coordinate system, Geographical distance, Latitude, Longitude and Reference ellipsoid.

• See the section for Coordinates above.

Magnitude

  quantity = "magnitude_of_" + [vector quantity]

  Examples

sea_water__magnitude_of_vorticity
sea_floor_water__magnitude_of_shear_stress

• 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 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.

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. A mask may be 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.

• The 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".

• A mask is sometimes associated with a threshold value and "threshold" is a quantity suffix. We could use a standard name like "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 Metadata File.

• Terms like "presence_mask", '"inclusion_mask" and "exclusion_mask" would fit the Process_name + Quantity Pattern.

• Note that painters use Masking tape to "mask off" areas that should not be painted.

• See: Binary image and Mask (computing).

Mass

  base_quantity = "mass"

  Examples

### cesium_atomic_mass   (also relative_atomic_mass = atomic_weight)
white_dwarf_star__chandrasekhar_limit_mass   (object = white_dwarf_star)
electron__relativistic_mass
electron__rest_mass   (also invariant mass, intrinsic_mass, proper mass)
neutron_star__tolman_oppenheimer_volkoff_limit_mass

• The SI units for mass are kilograms.

• What about "biomass"?

• See Attributes of Atoms, Concentration, Flux.

• See: Added mass, Biomass, Invariant mass, Mass-energy equivalence, Mass in special relativity, Planck mass and Transverse mass.

Maximum

  Examples

watershed_outlet_water__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 watershed discharge. It seems best to introduce "time_max_of_" and "domain_max_of_" as operations instead. See: CSDMS Operation Templates.

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.

Minimum

  Examples

watershed_outlet_water__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 watershed discharge. It seems best to introduce "time_min_of_" and "domain_min_of_" as operations instead. See: CSDMS Operation Templates.

Modulus

  base_quantity = "modulus"
  quantity = "bulk_modulus"
  quantity = "shear_modulus"
  quantity = "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: Shear modulus.

• See: Bulk modulus, Dynamic modulus, Elastic modulus, Lamé parameters, P-wave modulus, Poisson's ratio, Shear modulus and Young's modulus.

Number

  base_quantity = "number"
  quantity = "julian_day_number"
  quantity = "neutron_number"
  quantity = "proton_number"
  quantity = "quantum_number"
  quantity = "wave_number"
  quantity = "winding_number"

  Examples

carbon_isotope__neutron_number
iron_atom__neutron_number
iron_atom__proton_number
sea_water_surface_wave__number
vehicle__identification_number

• 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. However, dimensionless numbers also end with the word "number" as discussed in the Dimensionless Number template and they are typically not integers. Also the wave number need not be an integer.

• 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 quantum_numbers, including the: principal quantum number, azimuthal quantum number, magnetic quantum number, spin quantum number and topological quantum number.

• Several other "numbers" are defined in particle physics, such as the "electronic_number", "muonic_number" and "tauonic_number".

• The winding number is used in mathematics as an attribute of closed, planar curves.

• See: Atomic number, Lepton number and Neutron number.

• Unique identification numbers are often assigned to people and other objects. See Credit card number,Employer Identification Number (EIN), Enzyme Commission Number, National Identification Number, Numbering scheme, Social Security Number, Transporter Classification Number and Vehicle Identification Number (VIN).

• In the branch of mathematics called number theory there are many special numbers, often named after a famous person. The Online Encyclopedia of Integer Sequences (OEIS) maintains an extensive database of information on integer sequences. See: Bell number, Catalan number, Euler number, Fibonacci number, Hardy-Ramanujan number, Kaprekar number, Lucas number, Prime number and Smith number. Also see the template for Constants in Math.

• For hydrologic features such as rivers, unique identification numbers such as the USGS Hydrologic Unit Code (or "HUC number") and Pfafstetter Code are used. See Code.

• See the Count template and Julian day.

Parameter

  base_quantity = "parameter"

  Examples

earth__coriolis_parameter
channel_bed__shields_parameter

• Parameters often occur in empirical laws.

• The CSDMS standard names use "manning_coefficient" vs. "manning_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.

Partial Pressure

  base_quantity = "partial_pressure"
  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: 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:

surface_carbon_dioxide_in_air_and_carbon_dioxide_in_sea_water_partial_pressure_difference
(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.

Perimeter

  base_quantity = "perimeter"

  Examples

channel_cross-section__perimeter
watershed__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 Koch snowflake.

• See Diameter.

Period

  base_quantity = "period"
  quantity = "orbit_period" (see "Object vs. Adjective Rule")

  Examples

chicken-pox__incubation_period
earth__rotation_period
flood__expected_return_period    ######### Need a flood size adjective.
mars_orbit__sidereal_period
mars_orbit__synodic_period
sea_water_surface_wave__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: Return period, "return time", "recurrence interval" and "flood frequency" are used to quantify the expected time between floods of a given size.

• See: 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", gestation period, Hibernation period, incubation period, rotation period, "sleeping period"], waiting period and wave period.

• See Duration and Time.

pH

  base_quantity = "ph"

  Examples

acetic_acid__ph
channel_water__ph

• This quantity measures the 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: Wikipedia: pH.

Point

  Examples'

boiling_point
breaking_point  ??
bubble_point
critical_point   (See: Critical point.)
curie_point  (See: Curie point.)
dew_point
flash_point
freezing_point
frost_point
melting_point
wilting_point    (used in infiltration theory)
yield_point   (See: Yield strength.)

atmosphere_water__dew_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 CSDMS Process Names in front of "_point".

Porosity

  base_quantity = "porosity"

  Examples

soil__porosity

• Could also be called "soil_air__volume_fraction".

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: Stream power.

Precipitation

  quantity = "precipitation_" + base_quantity

  Examples

atmosphere_water__precipitation_duration
atmosphere_water__liquid_equivalent_precipitation_rate   (in liquid or solid form)
atmosphere_ice__precipitation_rate
atmosphere_snow__precipitation_rate
titan_atmosphere_methane__liquid_equivalent_precipitation_rate  (on Titan)

• Precipitation is not a quantity, but rather a process as defined at the top of the CSDMS Process Names page. However, there are several quantities associated with precipitation, as seen in the examples above. A "precipitation_rate" has units of [length / time] (e.g. mm 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__liquid-equivalent_precipitation_rate", which 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_rate" and "snow__melt_rate", since the process of melting converts ice and snow to liquid water.

• The name "snow__liquid_equivalent_depth" is also used and is computed by multiplying the "snow__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.

Pressure

  base_quantity = "pressure"

  Examples

channel_bed_water__hydrostatic_pressure
channel_bed_water__pressure  
channel_water__pressure       (anywhere in the channel)
earth_atmosphere__pressure
land_surface_air__pressure
    (also: earth_atmosphere_at_land_surface_pressure ??)

• Pressure may be thought of as "force per unit area".

• The quantity "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.

• Note that additional assumptions like "equilibrium" and "hydrostatic" could be left out of the name and instead provided using an <assume> tag in the metadata file, but they are currently allowed as modifiers in the quantity name also.

• 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 meteorology, the term "vapor pressure" is used to mean the partial pressure of water vapor in the atmosphere, even if it is not in equilibrium, and the adjective equilibrium is inserted otherwise. Our "object-in-object" pattern therefore prescribes using: "water_vapor_in_air_partial_pressure" instead of just "air_vapor_pressure". See Vapor Pressure.

• Electromagnetic radiation exerts radiation pressure on an illuminated surface. A 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.

• In cosmology, there is also a concept of "negative pressure".

• In geology, the term confining_pressure or overburden_pressure is used.

Process Attributes

  quantity = [ process name ] + [ base_quantity ]

  Examples

digestion_period, gestation_period, hibernation_period,
incubation_period, sleeping_period
-------------------------------------------------------------------
infiltration_rate, lapse_rate, melt_rate, precipitation_rate,
rainfall_rate  (use precipitation instead?)
    (Note:  "melt" -> "melting" ?)
-------------------------------------------------------------------
conception_date
delivery_date        (vs. "expected_delivery_date" or "due_date")
launch_date
ovulation_date
starting_date        (or "start_date" ??)
----------------------
rainfall_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

• Process names are almost always generated by converting a verb to a noun with a standard ending like "tion". See CSDMS Process Names for more details and a long list of examples.

• The base quantity "_rate" makes sense for most processes, but a given process if often naturally associated with other base quantities.

• 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")

• See the Rates of Processes template for examples where the base quantity is "rate".

Radiation

  quantity = "radiation_" + quantity

  Examples

incandescent_light_bulb__radiation_intensity   ? ##### CHECK
universe__cosmic_background_radiation_frequency
 
atmosphere__absorbed_incoming_shortwave_radiation_flux
atmosphere__reflected_incoming_shortwave_radiation_flux     (by aerosols or clouds)
atmosphere__transmitted_incoming_shortwave_radiation_flux  (sent to land surface)
atmosphere_aerosol__absorbed_incoming_shortwave_radiation_flux
atmosphere_aerosol__reflected_incoming_shortwave_radiation_flux
atmosphere_aerosol__transmitted_incoming_shortwave_radiation_flux
atmosphere_aerosol__downward_outgoing_longwave_radiation_flux   (emitted)
atmosphere_cloud__absorbed_incoming_shortwave_radiation_flux     (or "cloud_in_atmosphere" ?)
atmosphere_cloud__reflected_incoming_shortwave_radiation_flux
atmosphere_cloud__transmitted_incoming_shortwave_radiation_flux
atmosphere_cloud__downward_outgoing_longwave_radiation_flux  (emitted)
 
atmosphere_top-surface__incoming_shortwave_radiation_flux    ###### (outer_edge vs. top_surface?)
 
land_surface__backscattered_incoming_shortwave_radiation_flux
land_surface__diffuse_incoming_shortwave_radiation_flux
land_surface__direct_incoming_shortwave_radiation_flux
land_surface__incoming_longwave_radiation_flux      (incident and downward)
land_surface__outgoing_longwave_radiation_flux       (emitted and upward)
land_surface__net_longwave_radiation_flux          (net = incoming - outgoing;  it may be positive or negative)
land_surface__net_shortwave_radiation_flux         (net = incoming - outgoing;  it may be positive or negative)
 
land_or_sea_surface__net_shortwave_radiation_flux
   
sea_floor_surface__incoming_shortwave_radiation_flux
sea_surface__absorbed_incoming_shortwave_radiation_flux 
sea_surface__reflected_incoming_shortwave_radiation_flux
sea_surface__transmitted_incoming_shortwave_radiation_flux
sea_water__downward_incoming_shortwave_radiation_flux   (moving downward through the water)

• Note that "radiation" (the process of generating and sending out energy) and "irradiation" (the process of receiving energy from a source of radiation) 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.) In addition, the word "net" will be defined to mean "incoming - outgoing", and may be positive or negative. 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 examples above cover most of the Earth's basic radiation budget.

• 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 typically have units of [W m-2]. See the Flux template.

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: Bend radius, Bohr radius, Classical electron radius, Covalent radius, Earth radius (which gives several possible definitions), Filling radius, Ionic radius, Minimum Railway Curve Radius, Radius of curvature (mathematics), Schwarzschild Radius, Turning Radius, Van der Waals radius and Wigner-Seitz radius.

• What about Radius of Curvature? See the object template for Surface.

Rate of a Process

  quantity = [ process name ] + "_rate"

  Examples

air__temperature_lapse_rate
atmosphere_water__liquid-equivalent_precipitation_rate
glacier_terminus__calving_rate
human_alcohol__consumption_rate
ice__precipitation_rate
land_surface_water__evaporation_rate
land_surface_water__infiltration_rate
methane__liquid_equivalent_precipitation_rate   (on Titan)
snow__melt_rate
snow__precipitation_rate
vehicle_fuel__consumption_rate

• When necessary for clarification, the standard assumption name "liquid_equivalent" can be included with an <assume> tag in a Model Metadata file. It seems that the quantity "ice_melt_rate", however, implies a rate at which water is being generated. In the CF Standard Names, "lwe" is used as a standard abbreviation for "liquid_water_equivalent" and this abbreviation is used as an adjective.

• Note that "precipitation_rate" follows the Process_name + Quantity Pattern and is used in the examples instead of "icefall_rate", "rainfall_rate" and "snowfall_rate". 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 and the CSDMS Process Names.

Ratio

  base_quantity = "ratio"
  quantity_suffix = "ratio" (in some cases)
  quantity = "aspect_ratio"
  quantity = "mass_ratio"

  Examples

air_to_fuel__mass_ratio     (or "mixture_ratio")
bear__brain_to_body_mass_ratio
earth_ellipsoid__inverse_flattening_ratio
fuel_to_oxidizer__equivalence_ratio   ###
image__aspect_ratio
lithosphere__poisson_ratio
rocket_payload__mass_ratio
rocket_propellant__mass_ratio
 
channel_cross_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 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 Flattening.

• There are many ratios in economics, including "debt_to_credit_ratio", Debt ratio, Debt-to-GDP ratio, Debt-to-income ratio and Loan_to_value_ratio.

• See Fineness ratio, Mass ratio, Poisson ratio, Power-to-weight ratio and Ratio.

Reference Quantities

  quantity = "reference_" + quantity1 + "_" + quantity2
  quantity = quantity1 + "_reference_" + quantity2

  Examples

sea_surface_air__reference_pressure  ??   (insert "dry" before "reference"?)
sea_surface_air__reference_temperature ??
 
air__standard_refraction_index
 
wind__reference_height_speed
wind__speed_reference_height    ("reference" is between the quantities)
 
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 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 geopotential height are defined relative to Earth's mean sea level or MSL. An <assume> tag is needed to define the corresponding reference value.

• Georeferenced quantities, such as elevation, require specifying a 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 CSDMS Metadata Names page. They can be specified in a Model Metadata File using <ellipsoid>, <datum> and <projection> tags.

• In 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.

Scale

  quantity_suffix = "scale"
  quantity = "length_scale"
  quantity = "time_scale"
  quantity = "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: Length scale, Kolmogorov microscales, Batchelor scale and Taylor microscale.

• See Natural units, Planck units, Planck length and Planck time.

• Other interesting length scales include the Obukhov length,Mesoscopic scale, Synoptic scale and Nanoscale.

Sinuosity

  base_quantity = "sinuosity"
  quantity = "straight_sinuosity"
  quantity = "valley_sinuosity"

  Examples

channel_centerline__straight_sinuosity
channel_centerline__valley_sinuosity
valley_centerline__straight_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 call "valley 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. An alternative, which we call "straight sinuosity", 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 "straight sinuosity" will always be greater than or equal to "valley 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 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".

• See: Sinuosity, Tortuosity, Chord, Geodesic and Meander.

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: Solubility.

• 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.

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: List of spans,Maximum life span, Span (in architecture), Span (as a unit) and Wingspan.

Speed

  base_quantity = "speed"
  quantity = "escape_speed"
  quantity = "flow_speed"
  quantity = "settling_speed"
  quantity = "terminal_speed"

  Examples

channel_water__flow_speed
glacier_bed__sliding_speed
wind__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 process name "flow" is inserted in accordance with the Process_name + Quantity Pattern.

• "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.

• See Velocity for "escape speed", "settling speed" and "terminal speed".

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.

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 Newtonian fluid, there is a linear relationship between the shear stress and the strain rate.

• See Deformation, Shear stress, Strain rate and Stress-strain curve.

Stress

  base_quantity = "stress"
  quantity = "deviatoric_stress"
  quantity = "normal_stress"
  quantity = "shear_stress" (vs. "shearing_stress"; see below)

  Examples

channel_bed__magnitude_of_shear_stress
channel_bed__shields_critical_shear_stress
sea_floor_surface__normal_component_of_stress
sea_floor_surface__x_z_component_of_shear_stress
sea_water__downward_eastward_component_of_shear_stress
sea_water__downward_northward_component_of_shear_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 "eastward", "northward" and "upward" 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 CSDMS Process Names page. Many fluid dynamics textbooks use "shearing", e.g. Batchelor (1988), and "tangential stress" is a synonym.

• 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.

• In oceanography there is a concept of radiation stress and for electromagnetic radiation there is radiation pressure. See Pressure.

• There are 19 CF Convention 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

Temperature

  base_quantity = "temperature"
  quantity = "convective_temperature"
  quantity = "effective_temperature"
  quantity = "equivalent_temperature"
  quantity = "equivalent_potential_temperature"
  quantity = "potential_temperature"

  Examples

air_water-vapor__bubble_point_temperature
air_water-vapor__dew_point_temperature
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.

• See the Wikipedia pages for: Critical point, Curie point, Dew point, Hydrocarbon dew point, Bubble point and Flash point.

• See the Wikipedia pages for: Temperature, Equivalent temperature, Potential temperature, Equivalent potential temperature, Effective temperature, Color temperature, Brightness temperature, Atmospheric temperature, Sea surface temperature, Convective temperature, Dry-bulb temperature and Wet-bulb temperature.

Term

  base_quantity = "term"
  quantity = "acceleration_term"
  quantity = "convection_term"
  quantity = "diffusion_term"
  quantity = "forcing_term"
  quantity = "friction_loss_term"
  quantity = "sink_term"
  quantity = "source_term"
  quantity = "time_derivative_term" (or use "unsteady_term" instead?)

  Examples

convection_diffusion_equation__convection_term"
convection_diffusion_equation__diffusion_term"
navier_stokes_equation__body_force_term
navier_stokes_equation__convective_acceleration_term
navier_stokes_equation__pressure_gradient_term
navier_stokes_equation__unsteady_acceleration_term
navier_stokes_equation__viscosity_term    (or "viscous_diffusion_term" ?)
poisson_equation__laplacian_term
poisson_equation__source_term

• Many models allow various "terms" in an equation that the model solves numerically to be saved as output.

• In the 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 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 CSDMS Quantity Templates page and the list of CSDMS Process Names.

• This template is still under review. The appropriate object_name (possibly an equation_name from the 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: Field equation, Laplacian, Vector Laplacian, Poisson's equation, Pressure gradient and Shallow water equations.

Thickness

  base_quantity = "thickness"

  Examples

burgess_shale_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.

Threshold

  operation_prefix = "threshold"

  Examples

snow__threshold_of_degree-day-temperature  ### ??

• 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.

Time

  quantity_suffix = "time"

  Examples

channel_water__time_of_time_max_of_volume_flow_rate
earth_surface_mars__local_rise_time
earth_surface_mars__local_set_time
earth_surface_sun__local_rise_time
earth_surface_sun__local_set_time
earth_surface_venus__local_rise_time
earth_surface_venus__local_set_time
mars_surface_venus__local_rise_time
mars_surface_venus__local_set_time
model__run_time
model__start_time
model__stop_time
model__time

denver_horizon_mars__rise_time
denver_viewing_mars__rise_time
mars_viewed_from_denver__rise_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 CSDMS Process Names.

• In the mathematics of stochastic processes, the quantities: Hitting time and 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 "rising_time" and "setting_time" can be defined for any celestial body and an observing location on Earth. See the US Navy's astronomical data services page. Note that these quantities require specifying two objects.

• See: Residence time, Relaxation time, Transition time, Arrival time (and ETA), Fall time, Lead time, Rise time and Holding time.

• See Duration and Period.

Time Step

  quantity_suffix = "step"
  base_quantity = "time"
  quantity = "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.

Unit-width (and similar) Quantities

  quantity = base_quantity

  Examples

human_blood_red-cell__count-per-volume
land_surface_water__volume-per-unit-contour-length_flow_rate
sea_water_surface_wave_crestline__power-per-unit-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:

per_capita
per_unit_area
per_unit_length
per_unit_mass
per_unit_time
per_unit_width
 

These could all be used as adjective or modifier prefixes for a base quantity.

Velocity

  base_quantity = "speed"
  quantity = "darcy_speed"
  quantity = "drift_speed"
  quantity = "escape_speed"
  quantity = "fall_speed"
  quantity = "flow_speed"
  quantity = "group_speed"
  quantity = "impact_speed"
  quantity = "initial_speed"
  quantity = "phase_speed" (also called "celerity")
  quantity = "settling_speed"
  quantity = "terminal_fall_speed"

  base_quantity = "velocity"
  quantity = "darcy_velocity"
  quantity = "drift_velocity"
  quantity = "flow_velocity"
  quantity = "group_velocity"
  quantity = "impact_velocity"
  quantity = "initial_velocity"
  quantity = "phase_velocity"

  quantity = "azimuth_angle_of_velocity"
  quantity = "x_component_of_velocity"
  quantity = "y_component_of_velocity"
  quantity = "z_component_of_velocity"
  quantity = "zenith_angle_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__east_component_of_flow_velocity
sea_water__flow_speed
sea_water__north_component_of_flow_velocity
sea_water__x_component_of_flow_velocity
sea_water__y_component_of_flow_velocity
  
sea_water_internal_wave__group_speed
sea_water_internal_wave__phase_speed
sea_water_surface_wave__group_speed
sea_water_surface_wave__phase_speed
 
soil_water__x_component_of_darcy_velocity
soil_water__y_component_of_darcy_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", "local_azimuth_angle_of" and "local_zenith_angle_of". For 2D vector fields, only the azimuth angle applies, but for 3D vector fields the zenith angle (from spherical coordinates) is also required. See the 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 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 shear velocity, terminal velocity and 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 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: Angular velocity, Drift velocity, Flow velocity, Group velocity, Phase velocity, Proper velocity, Relative velocity, Soil mechanics (Darcy velocity) Stokes drift and Velocity.

• See the template for Speed.

Viscosity

  base_quantity = "viscosity"
  quantity = "dynamic_shear_viscosity"
  quantity = "dynamic_volume_viscosity"
  quantity = "eddy_viscosity"
  quantity = "extensional_viscosity"
  quantity = "kinematic_shear_viscosity"
  quantity = "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

• 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 volume viscosity which is important for compressible fluids but is less well-known than shear 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 Chapman-Enskog equation can be used. For liquids, several different models are available; see: 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 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 reciprical of viscosity is called fluidity.

• See: Viscosity, Inviscid flow, Large eddy simulation (LES), Newtonian fluid and Non-Newtonian fluid.

Voltage

  base_quantity = "voltage" [Volts = Joules per Coulomb]

  Examples

battery__voltage
electric-appliance__voltage
electric-fence__voltage

• See: Voltage and Voltage drop.

Vorticity

  base_quantity = "vorticity"
  quantity = "absolute_vorticity"
  quantity = "potential_vorticity"
  quantity = "relative_vorticity"

  Examples

sea_water__downward_component_of_vorticity     ## (use "flow_vorticity" instead ??)
sea_water__eastward_component_of_vorticity
sea_water__magnitude_of_vorticity
sea_water__northward_component_of_vorticity
sea_water__southward_component_of_vorticity
sea_water__upward_component_of_vorticity
sea_water__westward_component_of_vorticity
sea_water__x_component_of_vorticity
sea_water__y_component_of_vorticity
sea_water__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.

• Absolute vorticity is relative vorticity plus a term due to the Earth's rotation.

• Potential vorticity is absolute vorticity divided by the vertical spacing between levels of constant entropy.

• Since the curl of any gradient vector is zero, taking the curl of the Navier-Stokes equation eliminates the pressure gradient term.

• See Vorticity, Circulation and Vector calculus identities.

Wavelength

  base_quantity = "wavelength"
  quantity = "compton_wavelength"
  quantity = "reduced_compton_wavelength"

  Examples

airy-wave__wavelength
cnoidal-wave__wavelength
electron__compton_wavelength
sea_water_internal-wave__wavelength  (### or sea_internal_water_wave ??)
sea_water_surface-wave__wavelength      (### or sea_surface_water_wave ??)
sine-wave__wavelength
stokes-wave__wavelength

• The wavelength is the distance between successive crests or troughs in a periodic function.

• See the section called Attributes of Radiation above.

• See: Amplitude, Angular frequency, Compton wavelength, de Broglie wavelength, Frequency (and Period), Hertz, Thermal de Broglie wavelength, Wavelength, Wavenumber and Wave vector.

Weight

  base_quantity = "weight"
  quantity = "specific_weight"

  Examples

alaskan-black-bear__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: Specific weight and Weight.

Yield

  base_quantity = "yield"
  quantity = "specific_yield" (in groundwater modeling)

  Examples

watershed_sediment__yield

• In geology, "sediment yield" refers to the total mass of particulate matter (suspended or bedload) that reaches the outlet of a watershed over a fixed time interval. It has units of [mass / (area * time)] or [M L-2 T-1]. See: sediment yield.

• In agriculture, "crop yield" refers to the total amount produced (e.g. kilograms or bushels) per unit area. See: Crop yield and Yield (wine).

• What about "yield_strength" (plastic deformation) ? See: Yield (engineering).

• See also: Specific yield (groundwater), Yield (chemistry), Yield surface and Quantum yield.