Define standard name terms; determine which terms are synonyms

[mkavulich]

There are a lot of terms used in Standard Names that are not defined, and many of them do not have an obvious definition even in context. In addition, there seem to be many terms that could be synonyms (in which case they should be consolidated), but may have a distinct meaning depending on the context. This issue will list the standard names that need further clarification on what they are supposed to represent.

Definitions

• air_pressure_thickness Originally listed as pressure_thickness, this term does not appear in the CF standard names, and only occurs one in CCPP as pressure_thickness_at_Lagrangian_surface (with a few more instances of layer_pressure_thickness, which appears to be similar or related) but occurs 4 times in the standard names dictionary. With units of Pa listed, it is clearly distinct from the traditional synoptic definition (thickness between two pressure layers), but I can not find this term to be in common use, or a proper definition anywhere. "Cloud pressure thickness" appears to be a term used in radiation physics, but it is unclear to me if this is even the same concept, and regardless I was not able to find a good definition for that one either.
• atmosphere_heat_diffusivity This term appears often in EDMF contexts, but I have been unable to find a solid/common definition. It appears to be a different quantity to "thermal diffusivity" as defined in the AMS Glossary of Meteorology. It is listed under the CF standard names as "No help available" 😩

Potential synonyms

• cloud_condensate Appears to be a synonym for cloud_liquid_water, should we rename the former to the latter? If not a synonym, then we need to document the difference.
• heat_flux vs sensible_heat_flux vs temperature_flux; are these the same thing?

General definition questions

• Many PBL/SFC flux-related terms are implied to be "vertical flux", is this an assumption we can adopt?

[dudhia]

It is possible that pressure_thickness is layer_pressure_thickness where the clue would be if it dimensioned by the number of layers.

…

On Wed, Mar 26, 2025 at 9:42 AM Michael Kavulich ***@***.***> wrote: There are a lot of terms used in Standard Names that are not defined, and many of them do not have an obvious definition even in context. In addition, there seem to be many terms that could be synonyms (in which case they should be consolidated), but may have a distinct meaning depending on the context. This issue will list the standard names that need further clarification on what they are supposed to represent. Definitions - air_pressure_thickness Originally listed as pressure_thickness, this term does not appear in the CF standard names, and only occurs one in CCPP as pressure_thickness_at_Lagrangian_surface (with a few more instances of layer_pressure_thickness, which appears to be similar or related) but occurs 4 times in the standard names dictionary. With units of Pa listed, it is clearly distinct from the traditional synoptic definition ( thickness between two pressure layers), but I can not find this term to be in common use, or a proper definition anywhere. "Cloud pressure thickness" appears to be a term used in radiation physics, but it is unclear to me if this is even the same concept, and regardless I was not able to find a good definition for that one either. - atmosphere_heat_diffusivity This term appears often in EDMF contexts, but I have been unable to find a solid/common definition. It appears to be a different quantity to "thermal diffusivity" as defined in the AMS Glossary of Meteorology. It is listed under the CF standard names as "No help available" 😩 Potential synonyms - cloud_condensate Appears to be a synonym for cloud_liquid_water, should we rename the former to the latter? If not a synonym, then we need to document the difference. - heat_flux vs sensible_heat_flux vs temperature_flux; are these the same thing? General definition questions - Many PBL/SFC flux-related terms are implied to be "vertical flux", is this an assumption we can adopt? — Reply to this email directly, view it on GitHub <#105>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77DFR7YAJ66YFCWXNLL2WLDGXAVCNFSM6AAAAABZ2VM7TOVHI2DSMVQWIX3LMV43ASLTON2WKOZSHE2TAMBWG4ZTQNQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***> [image: mkavulich]*mkavulich* created an issue (ESCOMP/ESMStandardNames#105) <#105> There are a lot of terms used in Standard Names that are not defined, and many of them do not have an obvious definition even in context. In addition, there seem to be many terms that could be synonyms (in which case they should be consolidated), but may have a distinct meaning depending on the context. This issue will list the standard names that need further clarification on what they are supposed to represent. Definitions - air_pressure_thickness Originally listed as pressure_thickness, this term does not appear in the CF standard names, and only occurs one in CCPP as pressure_thickness_at_Lagrangian_surface (with a few more instances of layer_pressure_thickness, which appears to be similar or related) but occurs 4 times in the standard names dictionary. With units of Pa listed, it is clearly distinct from the traditional synoptic definition ( thickness between two pressure layers), but I can not find this term to be in common use, or a proper definition anywhere. "Cloud pressure thickness" appears to be a term used in radiation physics, but it is unclear to me if this is even the same concept, and regardless I was not able to find a good definition for that one either. - atmosphere_heat_diffusivity This term appears often in EDMF contexts, but I have been unable to find a solid/common definition. It appears to be a different quantity to "thermal diffusivity" as defined in the AMS Glossary of Meteorology. It is listed under the CF standard names as "No help available" 😩 Potential synonyms - cloud_condensate Appears to be a synonym for cloud_liquid_water, should we rename the former to the latter? If not a synonym, then we need to document the difference. - heat_flux vs sensible_heat_flux vs temperature_flux; are these the same thing? General definition questions - Many PBL/SFC flux-related terms are implied to be "vertical flux", is this an assumption we can adopt? — Reply to this email directly, view it on GitHub <#105>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77DFR7YAJ66YFCWXNLL2WLDGXAVCNFSM6AAAAABZ2VM7TOVHI2DSMVQWIX3LMV43ASLTON2WKOZSHE2TAMBWG4ZTQNQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[mkavulich]

Another term that seems ambiguous is "amount". It is used in several names, which use a number of different sets of units. All of these uses could plausibly be removed or replaced with a more specific term. Here I have removed the term where it doesn't hurt intelligibility, and replaced it with mass_content where a replacement is needed (analogous to energy_content which is already used for energy per unit area)

• cumulative_lwe_thickness_of_convective_precipitation_amount_between_sw_radiation_calls (units="m") --> cumulative_lwe_thickness_of_convective_precipitation_between_sw_radiation_calls
• lwe_thickness_of_rain_amount_on_dynamics_timestep_for_coupling (units="m") --> lwe_thickness_of_rain_on_dynamics_timestep_for_coupling
• lwe_thickness_of_snowfall_amount_on_dynamics_timestep_for_coupling (units="m") --> lwe_thickness_of_snowfall_on_dynamics_timestep_for_coupling
• canopy_water_amount (units="kg m-2") --> canopy_water_mass_content
• lwe_thickness_of_convective_precipitation_amount_on_previous_timestep (units="m") --> lwe_thickness_of_convective_precipitation_on_previous_timestep
• lwe_thickness_of_explicit_precipitation_amount_on_previous_timestep (units="m")--> lwe_thickness_of_explicit_precipitation_on_previous_timestep
• lwe_thickness_of_graupel_amount_on_previous_timestep (units="m") --> lwe_thickness_of_graupel_on_previous_timestep
• lwe_thickness_of_ice_precipitation_amount_on_previous_timestep (units="m") --> lwe_thickness_of_ice_precipitation_on_previous_timestep
• nonnegative_lwe_thickness_of_precipitation_amount_on_dynamics_timestep (units="m") --> nonnegative_lwe_thickness_of_precipitation_on_dynamics_timestep
• lwe_thickness_of_snowfall_amount_on_previous_timestep (units="mm") --> lwe_thickness_of_snowfall_on_previous_timestep
• surface_snow_amount_over_ice (units="kg m-2") --> surface_snow_mass_content_over_ice
• surface_snow_amount_over_land (units="kg m-2") --> surface_snow_mass_content_over_land
• lwe_thickness_of_surface_snow_amount (units="mm") --> lwe_thickness_of_surface_snow
• cumulative_lwe_thickness_of_convective_precipitation_amount_for_coupling (units="m") --> cumulative_lwe_thickness_of_convective_precipitation_for_coupling
• cumulative_lwe_thickness_of_precipitation_amount_for_coupling (units="m") --> cumulative_lwe_thickness_of_precipitation_for_coupling
• cumulative_lwe_thickness_of_snow_amount_for_coupling (units="m") --> cumulative_lwe_thickness_of_snow_for_coupling

I would propose the term amount be disallowed, and where necessary replaced with more specific terminology (as above), unless we can come up with a particular case where it is strongly needed.

[nusbaume]

Thanks for this issue @mkavulich! Just a few comments (and apologies for not responding sooner):

1. We use the term air_pressure_thickness in our CCPP-ized physics schemes, and were probably the ones who added it to the dictionary. I am not sure where the term originated, but I can say that mathematically it is simply the difference in air pressure (dp) between two vertical layers, so essentially:

   air_pressure_thickness = dp = p_i - p_i+1

   where "i" is for a vertical layer closer to the surface than "i+1". We definitely need a name for this quantity, but are happy to
   discuss a different name if that is preferred.

2. Is it possible that cloud_condensate includes both cloud liquid water and cloud ice, whereas cloud_liquid_water is only for the liquid component? If not then I imagine we'll eventually need a name for "all liquid and solid water mass in clouds".

3. I could imagine that heat_flux and sensible_heat_flux are synonyms (both should have units of W m-2), but I think temperature_flux is a different physical quantity (units of K m s-1 according to the dictionary). One could of course convert a heat flux into a temperature flux, but that would require dividing by the specific heat of whatever physical medium the flux is traveling through. We might also need to make a rule that if the physical quantity is actually a latent heat flux then that needs to be explicit (e.g. heat_flux is equivalent to sensible_heat_flux, but not latent_heat_flux).

Finally, I completely agree that "amount" is ambiguous and am happy to try and remove it whenever possible.