Version 1, 3 December 2008


Table of Contents

Characters
Spelling
Qualifications
Surface
Component
Medium
Process
Condition
Transformations
Special Phrases
Chemical Species
Generic Names

Most of the CF standard names in the Standard Name Table have been constructed following the guidelines described here, which have themselves drawn on the ECMWF and NCEP GRIB tables, the PCMDI standard variable names, and the NASA Global Change Master Directory . The guidelines may help to interpret the names and to suggest how new names could be derived. Please send requests and questions concerning standard names to the CF metadata mailing list.

Characters

Standard names consist of lower-letters, digits and underscores, and begin with a letter. Upper case is not used.

Spelling

US spelling is used e.g. vapor, sulfur.

Qualifications

Standard names may be qualified by the addition of phrases in certain standard forms and order. These qualifications do not change the units of the quantity. All of the following phrases in [] are optional. The words in typewriter type appear explicitly as stated, while the words in italic indicate other words or phrases to be substituted. The new standard name is constructed by joining the base standard name to the qualifiers using underscores.

[surface] [component] standard_name [at surface] [in medium] [due to process] [assuming condition]

Surface

A surface is defined as a function of horizontal position. Surfaces which are defined using a coordinate value (e.g. height of 1.5 m) are indicated by a single-valued coordinate variable, not by the standard name. In the standard name, some surfaces are named by single words which are placed at the start: toa (top of atmosphere), tropopause, surface. Other surfaces are named by multi-word phrases put after at: at_adiabatic_condensation_level, at_cloud_top, at_convective_cloud_top, at_cloud_base, at_convective_cloud_base, at_freezing_level, at_ground_level, at_maximum_wind_speed_level, at_sea_floor, at_sea_ice_base, at_sea_level, at_top_of_atmosphere_boundary_layer, at_top_of_atmosphere_model, at_top_of_dry_convection. The surface called "surface" means the lower boundary of the atmosphere. sea_level means mean sea level, which is close to the geoid in sea areas. ground_level means the land surface (beneath the snow and surface water, if any). cloud_base refers to the base of the lowest cloud. cloud_top refers to the top of the highest cloud. Fluxes at the top_of_atmosphere_model differ from TOA fluxes only if the model TOA fluxes make some allowance for the atmosphere above the top of the model; if not, it is usual to give standard names with toa to the fluxes at the top of the model atmosphere.

Component

The direction of the spatial component of a vector is indicated by one of the words upward, downward, northward, southward, eastward, westward, x, y. The last two indicate directions along the horizontal grid being used when they are not true longitude and latitude (if there is a rotated pole, for instance). If the standard name indicates a tensor quantity, two of these direction words may be included, applying to two of the spatial dimensions Z Y X, in that order. If only one component is indicated for a tensor, it means the flux in the indicated direction of the magnitude of the vector quantity in the plane of the other two spatial dimensions.

The names of vertical components of radiative fluxes are prefixed with net_, thus: net_downward and net_upward. This treatment is not applied for any kinds of flux other than radiative. Radiative fluxes from above and below are often measured and calculated separately, the "net" being the difference. Within the atmosphere, radiation from below (not net) is indicated by a prefix of upwelling, and from above with downwelling. For the top of the atmosphere, the prefixes incoming and outgoing are used instead.

Medium

A medium indicates the local medium or layer within which an intensive quantity applies: in_air, in_atmosphere_boundary_layer, in_mesosphere, in_sea_ice, in_sea_water, in_soil, in_soil_water, in_stratosphere, in_thermosphere, in_troposphere.

Process

The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. Possibilites are: due_to_advection, due_to_convection, due_to_deep_convection, due_to_diabatic_processes, due_to_diffusion, due_to_dry_convection, due_to_gravity_wave_drag, due_to_gyre, due_to_isostatic_adjustment, due_to_large_scale_precipitation, due_to_longwave_heating, due_to_moist_convection, due_to_overturning, due_to_shallow_convection, due_to_shortwave_heating, due_to_thermodynamics (referring to sea ice freezing and melting).

Condition

A phrase assuming_condition indicates that the named quantity is the value which would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the condition. Possibilities are assuming_clear_sky, assuming_deep_snow, assuming_no_snow.

Transformations

Standard names may be derived from other standard names (represented here by X, Y and Z) by the following rules. Successive transformations may be applied. Transformations may alter the units as shown.

RuleUnitsMeaning
change_over_time_in_X[X]change in a quantity X over a time-interval, which should be defined by the bounds of the time coordinate.
[horizontal_]convergence_of_X[X] m-1[horizontal] convergence of a vector X (i.e. the divergence multiplied by -1); if X does not have a vertical component then "horizontal" should be omitted.
correlation_of_X_and_Y[_over_Z]1correlation coefficient for variations (over Z e.g. time, longitude) of X and Y. X and Y are ordered alphabetically.
covariance_of_X_and_Y[_over_Z][X]*[Y]covariance for variations (over Z e.g. time, longitude) of X and Y. X and Y are ordered alphabetically.
component_derivative_of_X[X] m-1derivative of X with respect to distance in the component direction, which may be northward, southward, eastward, westward, x or y. The last two indicate derivatives along the axes of the grid, in the case where they are not true longitude and latitude.
derivative_of_X_wrt_Y[X]/[Y]dX/dY (keeping any other independent variables constant, i.e. the partial derivative if appropriate).
direction_of_Xdegreedirection of a vector, a bearing.
[horizontal_]divergence_of_X[X] m-1[horizontal] divergence of a vector X; if X does not have a vertical component then "horizontal" should be omitted.
histogram_of_X[_over_Z]1histogram (i.e. number of counts for each range of X) of variations (over Z) of X. The data variable should have an axis for X.
integral_of_Y_wrt_X[X]*[Y]int Y dX. The data variable should have an axis for X specifying the limits of the integral as bounds.
ln_X1natural logarithm of X. X must be dimensionless.
log10_X1common logarithm (i.e. base 10) of X. X must be dimensionless.
magnitude_of_X[X]magnitude of a vector X.
probability_distribution_of_X[_over_Z]1probability distribution (i.e. a number in the range 0.0-1.0 for each range of X) of variations (over Z) of X. The data variable should have an axis for X.
probability_density_function_of_X[_over_Z]1/[X]PDF for variations (over Z) of X. The data variable should have an axis for X.
product_of_X_and_Y[X]*[Y]X*Y. If X and Y are both scalars or both components of vectors, they are put in alphabetical order. If one of them is the component of a vector, it is put first i.e. the vector component is X, the scalar is Y.
ratio_of_X_to_Y[X]/[Y]X/Y.
square_of_X[X]*[X]X*X.
tendency_of_X[X] s-1derivative of X with respect to time.


Special Phrases

Some words and phrases have meanings which should be noted.

PhraseMeaning
anomalydifference from climatology
areahorizontal area unless otherwise stated
atmosphereused instead of in_air for quantities which are large-scale rather than local
condensed_waterliquid and ice
frozen_waterice
longwavelongwave radiation
lweliquid water equivalent
moisturewater in all phases contained in soil
oceanused instead of in_sea_water for quantities which are large-scale rather than local
shortwaveshortwave radiation
specificper unit mass unless otherwise stated
stpstandard temperature (0 degC) and pressure (101325 Pa)
toatop of atmosphere
unfrozen_waterliquid and vapour
waterwater in all phases if not otherwise qualified
wrtwith respect to


Chemical Species

The following names are used to identify chemical species in standard names.

Species
carbon_dioxide
dimethyl_sulfide
nitrate
nitrate_and_nitrite
nitrite
oxygen
ozone
phosphate
silicate
sulfate
sulfur_dioxide


Generic Names

The following names are used with consistent meanings and units as elements in other standard names, although they are themselves too general to be chosen as standard names. They are recorded here for reference only. These are not standard names.

UnitsGeneric Name
kg m-2amount
m2area
1area_fraction
1binary_mask
1data_mask
kg m-3density
Jenergy
J m-2energy_content
J m-3energy_density
s-1frequency
s-1frequency_of_occurrence
W m-2heat_flux
Wheat_transport
m2 s-1horizontal_streamfunction
m2 s-1horizontal_velocity_potential
kgmass
kg m-2 s-1mass_flux
1mass_fraction
1mass_mixing_ration
kg s-1mass_transport
1mole_fraction
mol m-2 s-1mole_flux
Pamomentum_flux
Papartial_pressure
speriod
Wpower
Papressure
1probability
W m-2radiative_flux
m2 s-2specific_eddy_kinetic_energy
m s-1speed
Pastress
Ktemperature
mthickness
m s-1velocity
m3volume
m s-1volume_flux
1volume_fraction
m3 s-1volume_transport
s-1vorticity