#153: Requires related to specific standard names
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Reporter: martin.juckes | Owner: cf-conventions@…
Type: enhancement | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords:
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Description changed by martin.juckes:
Old description:
> 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;
> data:
> 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
>
> == Radiances ==
>
> 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?
New description:
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.
It will take some time to complete the list. I propose that we add a
provisional list, after agreeing the format and approach, and work towards
completion later.
= 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.
== Required Coordinates ==
A common constraint involves the requirement that a particular coordinate
or set of coordinates be present.
The following table lists the rules and associated standard names. An
explanation of each rule follows below.
||||= Rule =||= Description =||
|||| ||= ''Standard Name(s)'' =||
|||| ||= '''Required coordinate(s)''' =||
|| 1 || Area Fraction || The fractional area in a cell covered by a
particulate area type. ||
|||| || ''area_fraction'' ||
|||| || '''area_type''' ||
|| 2 || Lifted from || Parameters defined in terms of lifting from a
reference level ||
|||| ||''atmosphere_convective_available_potential_energy,
atmosphere_convective_inhibition, atmosphere_level_of_free_convection,
atmosphere_lifting_condensation_level'' ||
|||| || '''original_air_pressure_of_lifted_parcel''' ||
|| 3 || Lifting range || Parameter defined in terms of lifting through a
specified range ||
|||| ||
''temperature_difference_between_ambient_air_and_air_lifted_adiabatically''
||
|||| ||
'''original_air_pressure_of_lifted_parcel,final_air_pressure_of_lifted_parcel'''
||
|| 4 || Radiances || For radiance variables a direction must be specified
||
|||| || ''downwelling_photosynthetic_photon_radiance_in_sea_water'' and
others
|||| || '''zenith_angle''' ||
|| 5 || Reference state || Variables which depend on reference air
temperature and humidity ||
|||| || ''mass_concentration_of_pm_*_ambient_aerosol_in_air,
mass_fraction_of_pm_*_ambient_aerosol_in_air'' ||
|||| || '''air_temperature, relative_humidity''' ||
|| 6 || Wavelength || Functions of wavelength ||
|||| || ''*_per_unit_wavelength_in_air'' ||
|||| || '''radiation_wavelength''' ||
In all cases, the structure follows the same pattern, illustrated by the
following examples for case 1. Area Fraction:
{{{
float cropcover(lat,lon);
cropcover:standard_name = 'area_fraction';
cropcover:coordinates = 'crop';
cropcover:units = '1';
character crop(nchar);
crop:standard_name = 'area_type';
data:
crop = 'crop';
}}}
== Other rules ==
=== Quantities representing a layer average or sum ===
Many "layer" quantities require vertical coordinates with bounds.
* ''*_atmosphere_layer[_*]'';
* ''*_ocean_layer[_*]'';
* ''*_soil_layer[_*]'';
=== 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).
{{{
float deltae(sig);
deltae:standard_name =
'change_in_energy_content_of_atmosphere_layer_due_to_change_in_sigma_coordinate_wrt_surface_pressure';
deltae:units = 'J m-2';
float sig(sig);
sig:axis = 'Z';
sig:standard_name = 'atmosphere_sigma_coordinate';
sig:bounds = 'sig_bnds';
sig:units = '1';
float sig_bnds(2,sig); # required because of _atmosphere_layer
}}}
=== Temporal change ===
Time rate of change or displacement over time require bounds on time
coordinate:
* ''change_over_time_*'';
* ''*_displacement'';
----
= Comments for discussion =
In some cases the wording of standard_name definitions could be
interpreted as a recommendation or suggestion rather than a requirement.
If some of these are intended only as suggestions, that should be flagged.
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Ticket URL: <http://cf-trac.llnl.gov/trac/ticket/153#comment:1>
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