Standard names: *Propose new names for AerChemMIP2 in CMIP7 which will be used to drive offline models*

[fmoconnor]

Proposer's name: Fiona O'Connor
Date: 20 December 2024

Here, on behalf of the Aerosol and Chemistry Model Intercomparison Project, I would like to propose a set of new names for use in CMIP7, albeit not for Fast Track. These names are to cover diagnostics from a few simulations (e.g., historical, scenarios), which will then be used to drive offline chemical transport models. The proposed names are as follows:

1. ocean_area_fraction
   Metadata: "Area fraction" is the fraction of a grid cell's horizontal area that has some characteristic of interest. It is evaluated as the area of interest divided by the grid cell area, or if the cell_methods restricts the evaluation to some portion of that grid cell (e.g. "where sea_ice"), then it is the area of interest divided by the area of the identified portion. It may be expressed as a fraction, a percentage, or any other dimensionless representation of a fraction.
   Units: 1

2. lake_area_fraction
   Metadata: "Area fraction" is the fraction of a grid cell's horizontal area that has some characteristic of interest. It is evaluated as the area of interest divided by the grid cell area, or if the cell_methods restricts the evaluation to some portion of that grid cell (e.g. "where sea_ice"), then it is the area of interest divided by the area of the identified portion. It may be expressed as a fraction, a percentage, or any other dimensionless representation of a fraction.
   Units: 1

3. stratiform_liquid_precipitation_flux
   Metadata: Stratiform precipitation is precipitation that formed in stratiform cloud. "Precipitation" in the earth's atmosphere means precipitation of water in all phases, but liquid precipitation refers to non-frozen water. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.
   Units: kg m-2 s-1

4. stratiform_solid_precipitation_flux
   Metadata: Stratiform precipitation is precipitation that formed in stratiform cloud. "Precipitation" in the earth's atmosphere means precipitation of water in all phases, but solid precipitation refers to that from frozen water. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.
   Units: kg m-2 s-1

5. convective_liquid_precipitation_flux
   Metadata: Convective precipitation is that produced by the convection schemes in an atmosphere model. "Precipitation" in the earth's atmosphere means precipitation of water in all phases, but liquid precipitation refers to non-frozen water. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.
   Units: kg m-2 s-1

6. convective_solid_precipitation_flux
   Metadata: Convective precipitation is that produced by the convection schemes in an atmosphere model. "Precipitation" in the earth's atmosphere means precipitation of water in all phases, but solid precipitation refers to frozen water. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.
   Units: kg m-2 s-1

7. tendency_of_mass_fraction_of_stratiform_cloud_ice_in_air_due_to_sublimation
   Metatdata: Mass fraction is used in the construction mass_fraction_of_X_in_Y, where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. Sublimation is the conversion of solid into vapor. In an atmosphere model, stratiform cloud is that produced by large-scale convergence (not the convection schemes). 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. "tendency_of_X" means derivative of X with respect to time.
   Units: kg kg-1 s-1

8. tendency_of_mass_fraction_of_convective_cloud_ice_in_air_due_to_sublimation
   Metatdata: Mass fraction is used in the construction mass_fraction_of_X_in_Y, where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. Sublimation is the conversion of solid into vapor. In an atmosphere model, convective cloud is produced by the convection schemes and not by large-scale convergence. 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. "tendency_of_X" means derivative of X with respect to time.
   Units: kg kg-1 s-1

9. Tendency_of_mass_fraction_of_stratiform_cloud_water_in_air_due_to_deposition_and_condensation
   Metadata: Mass fraction is used in the construction mass_fraction_of_X_in_Y, where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. Deposition is distinct from the processes of dry deposition and wet deposition of atmospheric aerosol particles, which are referred to in some standard names. In an atmosphere model, stratiform cloud is that produced by large-scale convergence (not the convection schemes). 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. "tendency_of_X" means derivative of X with respect to time.
   Units: kg kg-1 s-1

10. tendency_of_mass_fraction_of_convective_cloud_water_in_air_due_to_deposition_and_condensation
    Metadata: Mass fraction is used in the construction mass_fraction_of_X_in_Y, where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. Deposition is distinct from the processes of dry deposition and wet deposition of atmospheric aerosol particles, which are referred to in some standard names. In an atmosphere model, convective cloud is produced by the convection schemes and not by large-scale convergence. 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. "tendency_of_X" means derivative of X with respect to time.
    Units: kg kg-1 s-1

11. atmosphere_optical_thickness_due_to_liquid_water_in_cloud
    Metadata: The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-optical_thickness) on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. The atmosphere optical thickness applies to radiation passing through the entire atmosphere. "Cloud" means the component of extinction owing to the presence of liquid water. 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.
    Units: 1

12. atmosphere_optical_thickness_due_to_frozen_water_in_cloud
    Metadata: The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-optical_thickness) on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. The atmosphere optical thickness applies to radiation passing through the entire atmosphere. "Cloud" means the component of extinction owing to the presence of frozen water particles. 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.
    Units: 1

13. tendency_of_mass_fraction_of_water_in_air_due_to_convective_detrainment
    Metadata: Mass fraction is used in the construction mass_fraction_of_X_in_Y, where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. 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. "tendency_of_X" means derivative of X with respect to time.
    Units: s-1

14. surface_friction_velocity
    Metadata: A velocity is a vector quantity. Friction velocity is a reference wind velocity derived from the relationship between air density and downward stress and is usually applied at a level close to the surface where stress is assumed to be independent of height and approximately proportional to the square of mean velocity.
    Units: m s-1

15. mass_fraction_of_water_in_soil_layer_defined_by_root_depth
    Metadata: "Mass fraction" is used in the construction "mass_fraction_of_X_in_Y", where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The layer over which the quantity applies is that between the surface and the depth to which plant roots penetrate. A coordinate variable or scalar coordinate variable with standard name root_depth can be used to specify the extent of the layer. "Water" means water in all phases.
    Units: 1

16. mass_fraction_of_water_in_surface_soil_layer
    Metadata: "Mass fraction" is used in the construction "mass_fraction_of_X_in_Y", where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Water" means water in all phases.
    Units: 1

I look forward to the community discussion on these proposed names and I'm happy to respond to any queries.

Thanks,
Fiona O'Connor
On behalf of AerChemMIP2 in CMIP7

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[JonathanGregory]

Dear Fiona

Thanks for your proposals. They all conform to existing patterns, which helps a lot! Some comments:

• "Ocean area fraction" has the existing name sea_area_fraction.

• Is there a difference between "liquid precipitation" and "rainfall" (3 and 5)? We already have stratiform_rainfall_flux and convective_rainfall_flux.

• I suggest that condensation_and_deposition would be better than deposition_and_condensation, purely because it's alphabetical order! By following that rule we can reduce the chance of accidental duplication. The description of these names (9 and 10) don't say what deposition is, though they do explain what it isn't, which is helpful to avoid confusion.

• Just to check: by water (in 9 10 13), do you mean solid and liquid, not just cloud_liquid_water?

• For the optical thickness (11 and 12), is there a reason to say X_water_in_cloud rather than cloud_X_water as in other names? Can we say cloud_ice, as in other names, instead of cloud_frozen_water?

• There are existing standard names for components of friction velocity regarded as a vector, so for consistency we should clarify that your quantity (14) is a scalar. Also, we should clarify that it's for air, since friction velocity also applies to sea water. Hence I suggest magnitude_of_surface_friction_velocity_in_air.

• What is the "surface soil layer" (16)? If this simply means a soil layer whose upper boundary is the surface, I think it's better to say soil_layer, and use a depth coordinate to define the layer.

Best wishes and happy holiday

Jonathan

[taylor13]

Dear Fiona,

The name, lake_area_fraction has been discussed in another issue: #222. That discussion references previous discussions of the same thing. So, I suggest following the approach recommended there.

I agree with Jonathan that it is not clear what is meant by "deposition". I guess it is water in the solid or liquid state that falls out the bottom of any cloud layer examined. Or does it include cloud water that grows into droplets large enough to be considered "precipitation" but not necessarily immediately falling out of the layer?