Opened 3 years ago

Last modified 3 months ago

#153 new enhancement

Requires related to specific standard names — at Initial Version

Reported by: martin.juckes Owned by: cf-conventions@…
Priority: medium Milestone:
Component: cf-conventions Version:
Keywords: Cc:


This ticket is still under constrcution ......

A significant number of standard names contain, in their definitions, explicit specifications for additional required metadata. For instance, if the standard_name is "region" then there are constraints on the allowed values of the data variable. The standard name descriptions cannot include examples or markup, and the specification of the rules is not as clear as in the convention text. It also appears that the rules are not checked by the CF checker (at least not the few that I have looked at in detail) and I think the best way to get consistent checking would be to first create a well structured summary of these rules in the conventions document.

The specific proposal is add a new Appendix which lists the rules with examples where appropriate.

Appendix D: Rules associated with standard names

Some standard names bring additional constraints on the meta-data and/or data values of the variables they are associated with. This appendix list such names, grouped according to the types of constraint, and provides usage examples where needed.

The following table lists the rules and associated standard names. An explanation of each rule follows below.

=Rule= =Standard Name(s)=
1 Area Fraction area_fraction
2 Lifted from atmosphere_convective_available_potential_energy, atmosphere_convective_inhibition, atmosphere_level_of_free_convection, atmosphere_lifting_condensation_level
3 Lifting range temperature_difference_between_ambient_air_and_air_lifted_adiabatically
to be completed

Area fraction

Variables with standard name area_fraction require a coordinate with standard name area_type;

   float cropcover(lat,lon);
      standard_name: area_fraction;
      coordinate: crop
   character crop(nchar);
      standard_name: area_type;
      crop: 'crop';

Lifted from

atmosphere_lifting_condensation_level + 3 others: requires an original_air_pressure_of_lifted_parcel coordinate.

Lifting range

Quantities representing a layer average or sum

Many "layer" quantities (e.g. dry_static_energy_content_of_atmosphere_layer): require vertical coordinate with bounds.

Variation of variables in sigma coordinates due to surface pressure change

change_in_energy_content_of_atmosphere_layer_due_to_change_in_sigma_coordinate_wrt_surface_pressure: must have a vertical coordinate variable (axis=Z)

Time rate of change or displacement over time

change_over_time_... and .._displacement: require bounds on time coordinate


downwelling_photosynthetic_photon_radiance_in_sea_water and other radiance variables: direction must be specified, e.g. with coordinate of "zenith_angle".

Variables which depend on reference air temperature and humidity

mass_concentration_of_pm..._ambient_aerosol_in_air (and mass_fraction_of_pm..): require air_temperature and relative_humidity

Functions of wavelength

isotropic_radiance_per_unit_wavelength_in_air (and other per_unit_wavelength varables): the definition is slightly ambiguous with the sentence "A coordinate variable for radiation wavelength should be given the standard name radiation_wavelength" which, taken literally, means the use of a wavelength coordinate is optional: should it be "A coordinate variable for radiation wavelength should be given with the standard name radiation_wavelength", making the wavelength coordinate required?

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