Evspsbl of COSMO and ICON does not match the definition of water_evapotranspiration_flux – the dew and frost problem

[GeyerB]

The definition given in the CF Standard Names table for water_evapotranspiration_flux is

Water means water in all phases. "Evapotranspiration" means all water vapor fluxes into the atmosphere from the surface:
liquid evaporation, sublimation and transpiration.
Evaporation is the conversion of liquid or solid into vapor. Transpiration is the process by which liquid water
in plant stomata is transferred as water vapor into the atmosphere. (The conversion of solid alone into vapor is called "sublimation".)
In accordance with common usage in geophysical disciplines, "flux" implies per unit area,
called "flux density" in physics. Unless indicated in the cell_methods attribute, a quantity is assumed
to apply to the whole area of each horizontal grid box.
Unit: kg m-2 s-1

However, the variable for evapotranspiration in the output of COSMO-CLM and ICON-CLM also includes dew and hoarfrost formation, i.e. water flows from the atmosphere to the surface, which are not included in the definition. We suspect that this is common practice in climate modelling.
Up to now there is no CF standard_name for the flux of dew, frost, rime or condensation, although hydrologists would not tend to regard dew and frost as evaporation flows.
surface_downward_water_flux exists, but it also includes precipitation and refers to the entire surface water budget as flux (see below).
We would need something as water_evapotranspiration_flux_including_dew_and_frost – to come up with a well-thought-out proposal for CMIP7 would be certainly great…

For now we would vote for option 1 of possible solutions:

1. We could set an attribute “comment” for the variable evspsbl:
   “This variable includes not only evapotranspiration (as stated by the CF-conventions) but also water fluxes from the atmosphere to the surface associated with dew and frost formation.”
2. We withdraw the variable from ICON- and COSMO-CLM data sets.

Best regards,
Beate