Standard names: Propose new name for integrated surface snow mass for use in SIMIP and CMIP7

[pderepen]

On behalf of the Sea Ice Model Intercomparison Project (SIMIP) for CMIP7, I would like to propose a standard name for the integrated mass of snow over a certain region.

Name: surface_snow_mass Units: kg Description: Surface snow amount refers to the amount on the solid ground or on surface ice cover, but excludes, for example, falling snowflakes and snow on plants. The horizontal domain over which surface snow mass is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions.

Thanks for considering this proposal.

Proposer's name: Patricia DeRepentigny Date: 30 August 2024

[github-actions[bot]]

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 Patricia @pderepen

Thanks for your proposal. surface_snow_mass would be the area-integral of surface_snow_amount - is that right? It sounds fine to me. It's analogous to land_ice_mass and sea_ice_mass, for instance.

Best wishes

Jonathan

[pderepen]

Dear Jonathan @JonathanGregory

That is exactly right! We would like something analogous to land_ice_mass and sea_ice_mass but for surface snow to be able to evaluate the total mass of the cryosphere.

Best, Patricia

[JonathanGregory]

Yes, that makes sense! Thanks. Jonathan

[taylor13]

Not relevant to the standard name discussion, but for the CMIP7 list of requested output, I think it would be much better to obtain the surface_snow_amount, since the geographical distribution of snow mass will be needed for many studies. It is not difficult to compute the total mass of snow over a region by then integrating surface_snow_amount. This shifts the burden from the modeling groups to the user, which I think is appropriate in this case.

[pderepen]

@taylor13 Thank you for the comment. In the CMIP7 (and CMIP6) list of requested output, we already have the variable sisnmass which represent the total mass of snow on sea ice divided by sea-ice area. With this, one would be able to compute the total mass of snow over a region. Interestingly, this variable is associated to the CF standard name liquid_water_content_of_surface_snow and not surface_snow_amount. I must admit that it's not clear to me which of the two is better suited to sisnmass, but if you have a strong opinion about it I would suggest you submit a comment about this here: https://bit.ly/CMIP-MIP-variable-comment

Regarding only having the gridded snow mass and not the hemisphere-integrated value to alleviate the burden on the modeling centers, we (as co-chairs of SIMIP) believe that these integrated values are actually very helpful to the users (the integrated sea ice variables were the most downloaded in CMIP6 by a large margin) and also prevent some user errors when integrating (e.g., multiplying by grid area instead of sea-ice area). And since this is a relatively small and simple term to compute for the modeling centers, we think it won't increase their burden significantly.

Hope this helps!

[JonathanGregory]

liquid_water_content_of_surface_snow refers to the liquid water which is contained within the snowpack. That's not the same thing as lwe_thickness_of_surface_snow_amount, which converts surface_snow_amount (kg m-2) into thickness (m) using the density of liquid water. I suspect that sisnmass has the wrong standard name.

[taylor13]

Jonathan is right. I reviewed all the CMIP6 variables and this was one of quite a few that was almost certainly named incorrectly. I will post more on the data request site given above.

[pderepen]

@JonathanGregory @taylor13 Thanks to you both, I believe you are correct that the CF standard name for sisnmass should be surface_snow_amount and not liquid_water_content_of_surface_snow. I will submit a comment to rectify this in the CMIP7 data request.