CSN Quantity Templates

  CSDMS Standard Names — Quantity Templates

• The "templates" listed here are not exhaustive, but they do address many commonly needed cases where the pattern may not be obvious. Additional templates can be created from any of the "base quantities" listed in the text file "CSDMS_Standard_Name_Quantities.txt".
  
  

• 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 the best word choice here; see its Wikipedia page. The word "attribute" is a more general and may also be a good choice, but many attributes cannot be measured or quantified with a numerical value that has units. We could potentially use a "has units" metadata flag to indicate when an attribute is a quantity. A partial list of base quantities is given in the text file: "CSDMS_Standard_Name_Quantities.txt".
  
  

• A quantity suffix is a quantity name like "anomaly", "component", "increment" or "magnitude" that produces a new quantity name from an existing base quantity name. Note that an "increment" can be associated with any quantity to create an new quantity.
  
  

• For quantities that require 2 objects/substances to be specified, such as "partial_pressure", "solubility" and "volume_fraction" we reserve the word "_in_" and use the pattern: object = object + "_in_" + object

carbon_dioxide_in_air_partial_pressure
carbon_dioxide_in_water_solubility
clay_in_soil_volume_fraction
sand_in_soil_volume_fraction
silt_in_soil_volume_fraction

• There are several terms that may provide a "short name" or synonym for another quantity, such as:

aspect    = surface_gradient_direction
discharge = volumetric_flow_rate
slope     = surface_gradient_magnitude
speed     = velocity_magnitude   (or even "motion_rate")

• It may be beneficial to allow various standard abbreviations in quantity names. Possible examples are: stp = standard temperature and pressure and toa = top of atmosphere (used in CF).
  
  

• We may need a provision to indicate whether a vector quantity associated with a model grid cell is "incoming" or "outgoing". These adjectives are used in many CF Standard Names, but not with respect to a model cell. We may be able to use a "quantity_suffix" for these cases. While we could use modifiers like "from_cell", "into_cell" and "in_cell", it seems that we should avoid standard names that refer to a model cell in this way.

Altitude

  base_quantity = "altitude"

  Examples

airplane_altitude
skydiver_altitude

• The word "altitude" is reserved for objects that are above and not in contact with the land surface. (e.g. aircraft, air parcel, balloon) See the Elevation template. By contrast, "altitude" is used as a synonym for "elevation" in the CF Standard Names.

• What about the standard term "equilibrium_line_altitude" (ELA) ?

Angle

  base_quantity = "angle"

  Examples

azimuth_angle, bank_angle, bond_angle, declination_angle,
earth_axis_tilt_angle,  friction_angle, incidence_angle,
pitch_angle, polarization_angle, repose_angle, roll_angle,
rotation_angle, scattering_angle, slope_angle,
torsion_angle, yaw_angle, zenith_angle

• Some of these examples are in CF Standard Names.

• Note that "earth_axis_tilt_angle" uses the object name "earth_axis" to refer to a "part" of the Earth and "tilt_angle" follows the (process_name + quantity) pattern. (tilt vs. tilting) However, "earth_axial_tilt_angle" uses the modifier "axial" to convey the same concept. We need a rule to decide between such cases. The first version seems preferable.

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

• Maybe we should always use "aspect_angle" vs. "aspect" for clarity since we distinguish between "slope" and "slope_angle" ?

• bank_angle is related to banking (e.g. aircraft) in turns but may also be used in the context of channel banks. The object part of the name allows the same quantity name to be used in different contexts.

Anomaly

  quantity_suffix = "anomaly"

  Examples

air_pressure_anomaly

• Means the difference from climatology in CF Standard Names.

• This is a quantity suffix that creates a new quantity from an existing base quantity like elevation or pressure. Others are Component, Increment and Magnitude.

• Used in 4 CF Standard Names, namely:

air_pressure_anomaly
air_temperature_anomaly
geopotential_height_anomaly
surface_temperature_anomaly

Attributes of Atoms

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

  Examples

cesium_atom_proton_number
cesium_atom_characteristic_oscillation_frequency
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.

• See the [CSN_Object_Templates | CSDMS Object Template] for Atoms, Compounds, Ions and Molecules below for more details and examples.

Attributes of Planets

  quantity = attribute

  Examples

earth_axis_tilt_angle               (or axial_tilt_angle ??)
earth_ellipsoid_equatorial_radius
earth_ellipsoid_flattening_ratio
earth_ellipsoid_polar_radius
earth_orbital_eccentricity     (or just earth_orbit_eccentricity ??)
earth_rotation_rate
earth_rotational_period
earth_sidereal_day
mars_mean_diameter 

• These are often needed for proper georeferencing or modeling solar radiation via celestial mechanics.

• Notice that the word "ellipsoid" was inserted in the first three examples above. This illustrates another rule: If the quantity is not necessarily well-defined for the object itself (i.e. earth) but pertains more to another object being used to model that one, both object names are used, as in "earth_ellipsoid". This rule also appears in the case of channel cross sections that are modeled as trapezoids. In that case, every channel cross section has a well-defined perimeter, but only trapezoid-shaped cross-sections have a well-defined bottom width and bank angle.

Attributes of Processes

• See the template for Process Attributes.

Attributes of Products of a Company

  quantity = attribute

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

Capacity

  base_quantity = "capacity"

  Examples

air_thermal_capacity
pure_iron_thermal_capacity   (should we add "pure" here? ######)
snow_thermal_capacity
soil_thermal_capacity

• "thermal_capacity" seems preferable to and more precise than "heat_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. In our system, quantities like "water_content" associated with "field_capacity" would be given as: "field_capacity_water_content" or perhaps "at_field_capacity_water_content".

Coefficient

  base_quantity = "coefficient"

  Examples

diffusion_coefficient
kinetic_friction_coefficient
static_friction_coefficient

• Coefficients often occur in empirical laws.

• See Constants, Exponents, Indexes, Numbers, Parameters

Component of a Vector

  quantity_suffix = "component"
  quantity = [ direction adjective ] + [ vector quantity ] + "_component"

  Examples

x_axis_velocity_component,
eastward_velocity_component

• We could also use the pattern:
    quantity = [ vector quantity ] + [ direction ] + "_component"
  but the above pattern seems preferable.

• This is a quantity suffix that creates a new quantity from an existing base quantity (like a vector or tensor). See Anomaly, Increment and Magnitude.

• Note that "x_axis_" is used instead of just "x_". It might be interesting (and seems consistent) to introduce a word like "xward".

Concentration

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

• There are four main types of concentration, shown above, and they all have different units.

• There are many related concepts such as:
  molality, mole_fraction, mole_ratio, mass_fraction and mass_ratio.

• What about "osmotic_concentration" ?

Conductivity

  base_quantity = "conductivity"
  quantity = "electrical_conductivity" [siemens m-1] or [ohm-1 m-1]
  quantity = "hydraulic_conductivity" [m s-1]
  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, specify the assumption "_assuming_isotropic_medium" in the metadata.

Constants in Math

  base_quantity = "math_constant"  ?? ##########

  Examples

pi_math_constant

• This includes numbers like "pi", "phi" and "e".

• These numbers are not a quantity associated with an object like our others and should perhaps be excluded. However, one model may want to check the number of significant digits of pi that are used in another model, for example.

Constants in Physics

  base_quantity = "constant"

  Examples

avogadro_constant           [unit mol-1]   (see Note below)
dielectric_constant         [1]            (can be complex; = static_relative_permittivity)
gravitational_constant      [m s-2]
latent_heat_fusion_constant [J kg-1]       (similar for vaporization)
light_speed_constant        [m s-1]
planck_constant             [J s]
solar_constant              [W m-2]        (solar_irradiation_constant may be better)
spring_constant             [kg s-2]       (in Hooke's Law)
von_karman_constant         [1]

• The modern name for "Avogadro's number" is the "avogadro_constant". (See wikipedia). 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 refractive 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. Perhaps something like: "visible_light_in_air_speed" (a bit confusing, but follows the "_in_" pattern) or "visible_light_speed_in_air". In the latter, "in_air" is treated as an assumption/condition which instead could be included with metadata.

Content

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

  Examples

soil_saturated_water_content
snow_cold_content  ? (must be overcome before melting starts to occur)
snow_thermal_energy_content

• 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 Wikipedia: Water Content.

• Do we want to distinguish between:

gravimetric_water_content
volumetric_water_content

• Here are some additional types of "soil_water_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

• Many CF Standard Names containt 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.

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".

Density

  base_quantity = "density"

  Examples

air_density
air_stp_density   (stp = standard temperature and pressure)
sea_water_density

• 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".

Depth

  base_quantity = "depth"

  Examples

channel_water_mean_depth  ??
sea_water_depth  (or sea_floor_depth ?? #######)
secchi_depth
water_table_depth

• Measured as a positive downward distance below a reference surface.

• CF Standard Names often use "thickness" instead of "depth".

• See Elevation, Height, Thickness.

Diffusivity

  base_quantity = "diffusivity"
  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.

Dimensionless Numbers

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

  Examples

courant_number
froude_number
mach_number
reynolds_number
richardson_number

• Some names, like "Reynolds", end in "s", but don't add a possessive "s" at the end.

• 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.

• The modern name for "Avogadro's number" is the "Avogadro constant" and it is not dimensionless.

• There are quantities called "wave_number" (from wave theory) and "winding_number" (from math) that are not dimensionless numbers.

• See the Attributes of Atoms template for a discussion of "atomic_number" vs. "proton_number".

• In number theory (a branch of mathematics) there are many special numbers (or types of numbers) named after a famous person, such as: Bell, Catalan, Euler, Fibonacci, Kaprekar, Lucas, and Smith. Some, like Euler's number, are math constants like pi.

• Outside of science/math, we also have "social_security_number" and "tracking_number", "taxpayer_ID_number", etc.

Discharge or Volumetric Flow Rate

  quantity = "discharge" (OR "volumetric_flow_rate" ?) (see Wikipedia)

  Examples

channel_sediment_discharge
channel_water_discharge [m3 s-1]
channel_sediment_discharge
watershed_outlet_discharge [m3 s-]

• Units are [m3 s-1] and typical notation is "Q".

• It appears that a "volumetric_flux" should have units of [m3 m-2 s-1] = [m s-1], as in Darcy's Law. Discharge is then the integral of a volumetric flux over the cross-sectional area of a channel or pipe. See the notes for the Flux templates below.

• Avoid "streamflow" and "outflow" as synonyms for "discharge" or else define them to be aliases.

• Hydrologists also use "unit_width_discharge" or "discharge_per_unit_width", usually denoted by lower-case "q", with units of [m2 s-1].

Distance

  base_quantity = "distance"

  Examples

earth_to_sun_mean_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. Should we then introduce "_to_" as a special keyword for distances? The keyword "_to_" could similarly be be used for ratios. See "Ratios".

Duration

  base_quantity = "duration"

  Examples

rainfall_duration
sunshine_duration

• Typically preceded by a process name modifier. See CSDMS Process Names for a list of process names.

• Avoid the pattern "duration_of".

Elevation

  base_quantity = "elevation"

  Examples

bedrock_surface_elevation
land_surface_elevation
sea_surface_elevation
water_table_surface_elevation

• The word "altitude" is reserved for objects that are above and not in contact with the land surface. (e.g. aircraft, air parcel, balloon)

• See Altitude, Depth, Height, Thickness.

Exponent

  base_quantity = "exponent"

  Examples

sediment_transport_law_slope_exponent  ?? ##########

• Exponents often occur in empirical laws.

• See Coefficients, Constants, Indexes, Numbers, Parameters

Flux of Heat or Energy

  base_quantity = "flux"

• "Flux" can be viewed as "surface bombardment rate". See the Wikipedia article on "Flux".

• In CF Standard Names, "flux" implies per unit area. They say that "flux_density" is used in physics instead. However, "discharge" is a hydrologic flux with units [m3 s-1].

• In 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 "heat", "longwave", "shortwave" and "radiative".

• Most energy fluxes in atmospheric models have units of [W m-2].

Flux of Mass

  quantity = "mass_flux"

• In CF Standard Names, units are [kg m-2 s-1].

• See Concentrations, Discharges.

Flux of Momentum

  quantity = "momentum_flux"

• "momentum_diffusivity" [m2 s-1] is a nickname for kinematic_viscosity

• In CF Standard Names, units are [Pa].

Fraction

  quantity = "area_fraction"
  quantity = "volume_fraction"

  Examples

burned_area_fraction
cloud_area_fraction
forested_area_fraction   ??
land_area_fraction
sea_area_fraction
vegetation_area_fraction
void_volume_fraction   (see porosity)

• Used in 18 CF Standard Names and dimensionless. Some of these examples are CF Standard Names.

• There are 11 CF Standard Names that use "volume_fraction", also dimensionless. These 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 
 
However, hydrologists typically use the shorter term "soil_water_content" instead of "volume_fraction_of_condensed_water_in_soil".

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
gm_hummer_fuel_consumption_rate
gm_hummer_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: Wikipedia: Fuel efficiency of vehicles and Wikipedia: Efficient energy use.

Humidity

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

  Examples

air_relative_humidity

• The more general term for relative humidity (when not talking about water vapor in air) is relative_saturation.

Increment

  quantity_suffix = "increment"

  Examples

air_pressure_increment
bedrock_surface_elevation_increment

• This can be used for the change in a quantity that occurs over some time period, such as a model time step. It can be either negative or positive.

• This is a quantity suffix that creates a new quantity from an existing base quantity like elevation or pressure. Others are Anomaly, Component and Magnitude.

• See the Time Step template.

Index

  base_quantity = "index"

  Examples

diversity_index
normalized_difference_vegetation_index
palmer_drought_severity_index
price_index
refractive_index
soil_moisture_index
wetness_index  (with prefix: soil, topographic, catchment, etc.)

• See Coefficients, Constants, Exponents, Numbers, Parameters

  Limit

  Examples

chandrasekhar_limit    (object_white_dwarf_star)
high_frequency_limit   (in human hearing;  object = human_hearing ??)
tolman_oppenheimer_volkoff_limit  (object = neutron_star)

• The two limits above named after people should probably not be used by themselves, but should have the extra suffix "_mass". There is also a related "Schwarzchild radius"; see Radius.

• It is not clear that "_limit" would ever be used by itself. See Point.

• "cutoff" or "threshold" may sometimes be used similarly.

• See Radius.

Magnitude

  quantity_suffix = "magnitude"
  quantity = [ vector quantity ] + "_magnitude"

  Examples

vector_magnitude
normal_stress_magnitude   (or normal_stress_component_magnitude ??)
shear_stress_magnitude
stress_tensor_magnitude ??  #########

• Magnitude is a general term in mathematics, used to indicate a scalar-valued "size" of something like a vector or complex number.

• Exception: Use "speed" instead of "velocity_magnitude".

• This is a quantity suffix that creates a new quantity from an existing base quantity (like a vector or tensor). Others are Anomaly, Component and Increment.

• In CF Standard Names, "magnitude_of_" is a transformation (prefix) that is used in about 5 names.

Mass

  base_quantity = "mass"

  Examples

atomic_mass  (also relative_atomic_mass = atomic_weight)
chandrasekhar_limit_mass   (object_white_dwarf_star)
relativistic_mass
rest_mass (also invariant mass, intrinsic_mass, proper mass)
tolman_oppenheimer_volkoff_limit_mass  (object = neutron_star)

Miles per Gallon

• This is not allows 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.

Parameter

  base_quantity = "parameter"

  Examples

coriolis_parameter
manning_roughness_parameter

• Parameters often occur in empirical laws.

• See templates for Coefficient, Constant, Exponent, Index and Number.

Partial Pressure

  quantity = [substance 1] + "_in_" + [substance 2] + "_partial_pressure"

  Examples

carbon_dioxide_in_air_partial_pressure
water_vapor_in_air_partial_pressure      ##### (check)

• These are special in that two objects (substances) are involved. We reserve the word "_in_" for these cases. See Solubility.

• 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)

• Here are some possible alternative constructions for the CF Standard Name:
  surface_partial_pressure_of_carbon_dioxide_in_air
  that maintain our pattern of: [object] + [quantity]:

carbon_dioxide_in_air + _partial_pressure   (preferred ??)
carbon_dioxide_ + partial_pressure_ + in_air
atmospheric_carbon_dioxide_ + partial_pressure (at_surface?)
    (Here atmospheric implies "in air".)
in_air_carbon_dioxide_ + partial_pressure
air_contained_carbon_dioxide_ + partial_pressure
boa_carbon_dioxide + _partial_pressure
     (Here we introduce "boa = bottom_of_atmosphere" to match "toa" already used in the CF Standard Names.

• An alternate pattern that doesn't seem general enough is:
  quantity = "atmospheric_" + [substance] + "_partial_pressure"

• The word "equilibrium" may be inserted just before "partial_pressure".

Point

  base_quantity = "point"

  Examples

boiling_point
breaking_point  ??
dew_point
freezing_point
melting_point
wilting_point    (used in infiltration theory)

• The "point" at which something happens; a threshold.

• Each of the examples above puts a "process name" prefix, from the list of process names in CSDMS Process Names in front of "_point".

• Note that most of these is generally used as a modifier to the base quantity "temperature". It is not clear that "point" would ever be used by itself. See Limit.

• "limit" and "threshold" are used similarly. See Limit.

Porosity

  base_quantity = "porosity"

  Examples

soil_porosity

• Could also be called "void_volume_fraction".

Pressure

  base_quantity = "pressure"

  Examples

channel_bed_water_hydrostatic_pressure
channel_bed_water_pressure  
channel_water_pressure       (anywhere in the channel)
earth_atmosphere_pressure
    (also: earth_atmosphere_at_land_surface_pressure ??)
water_vapor_in_air_equilibrium_partial_pressure  (i.e. vapor_pressure)
water_vapor_in_air_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 Wikipedia: Vapor Pressure.

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

• Pressure may require specifying a single object (e.g. air) or two different objects. See Partial Pressure.

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")

• For a discussion of cases where the base quantity is "rate", see "Rates of Processes" below.

Radius

  base_quantity = "radius"

  Examples

earth_ellipsoid_equatorial_radius
earth_ellipsoid_polar_radius
schwarzchild_radius  (black_holes)
turning_radius

Rates of Processes

  quantity = [ process name ] + "_rate"

  Examples

air_temperature_lapse_rate
alcohol_consumption_rate
fuel_consumption_rate
rainfall_rate  ###### (avoid ? see notes.)
snow_precipitation_rate
surface_evaporation_rate
surface_infiltration_rate
surface_snow_melt_rate        ("melt" -> "melting" ??)
water_precipitation_rate

• For a "melt_rate", we may want to insert a modifier that indicates "liquid_water_equivalent", as in "lwe_melt_rate". (Or assume it is implied?) I think CF Standard Names use an assumption suffix for this like "assuming_liquid_water_equivalent".
  ############## CHECK

• The term "rainfall_rate" is commonly used and is better than "rain_rate" since rain is an object and not a process. The same applies to the terms snowfall and icefall. However, "rainfall" is a contraction of object (rain) and process (falling) names. A more general approach that adheres to our object-quantity pattern (with quantity as a process rate) is to use terms like:

ice_precipitation_rate
liquid_methane_precipitation_rate   (on Titan)
snow_precipitation_rate
water_precipitation_rate   (liquid_water ??)

• Note that "rainfall_rate" is used instead of "rain_rate", since rain is an object and not a process. The same for snowfall. But what is the appropriate object here? It could be "rain", but "rain" has been pulled into the process name (vs. "rain_falling_rate").

Ratio

  quantity = "ratio"

  Examples

brain_to_body_mass_ratio
charge_to_mass_ratio
channel_cross_section_width_to_depth_ratio
rocket_payload_mass_ratio
rocket_propellant_mass_ratio

• Ratios sometimes make reference to 2 objects as in the example. We could introduce "_to_" as a keyword for this purpose.

• These will generally be dimensionless. In fact, most dimensionless numbers are ratios of forces, etc.

• Perhaps we could replace the standard name:
  - channel_bed_relative_roughness_ratio to
  - channel_bed_roughness_length_to_water_depth_ratio

• "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.

• See Animals object pattern.

Solubility

  base_quantity = "solubility"

  Examples

carbon_dioxide_in_water_solubility

• These are special in that *two* objects (substances) are involved. We reserve the word "_in_" for these cases. See Partial Pressure.

Strain

  base_quantity = "strain"

• Strain is a deflection, with units of length

Stress

  base_quantity = "stress"
  quantity = "normal_stress"
  quantity = "shearing_stress" ("shearing" seems preferable to just "shear")

• Note that a quantity suffix like "component" or "magnitude" may be inserted after the word "stress" when it removes ambiguity. Absence of the suffix implies magnitude.

• 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".

• There are 19 CF Standard Names that contain "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"

  Examples

boiling_point_temperature
dew_point_temperature
freezing_point_temperature
melting_point_temperature
snow_temperature
soil_temperature

• Use "dew_point_temperature" vs. "temperature_at_dew_point". Similarly for "boiling_point", "melting_point", "freezing_point", etc.

• Can include how measured with assumptions in metadata.

Time

  quantity_suffix = "time"

  Examples

channel_reach_peak_outgoing_water_discharge_time

• Can be used as a "quantity suffix" associated with an event like reaching a peak value.

Time Step

  base_quantity = "_time_step_size" (OR "time_increment" ##########)

  Examples

model_time_increment

• We could also use: base_quantity = "_time_step_size" (vs. just "time_step") but we are using "increment" as part of a more general pattern.

Unit-width Quantity

  quantity = "unit_width_" + base_quantity

  Examples

surface_water_unit_width_discharge   (begin with "surface" ??)

• CF Standard Names use "_across_unit_distance" and "_across_line" to handle this concept.

• What about "power_per_unit_length_of_wave_crest" ?

• "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.