add "polarcap" grid for cesm3 release

[adamrher]

Description of changes

CTSM PR for installing the POLARCAP grid in CESM.

Specific notes

All I did is replicate all the entries for ARCTICGRIS in namelist_defaults_ctsm.xml, which has year 1850, 2000, 1979-2026 support. It also has support for 6 combinations of atm/lnd physics (clm50, clm51, clm60) x (CAM6; CAM7). @ekluzek @samsrabin as the POLARCAP grid is new to CESM, I don't know that we need to support these older versions of atm/lnd physics, but I'm not necessarily opposed to them either. I'm flexible and will just defer to yall.

Surface datasets were generated with tag ctsm5.2.005.

Contributors other than yourself, if any: None

CTSM Issues Fixed (include github issue #):
Fixes #2386

Are answers expected to change (and if so in what way)? Not unless you're running this new grid.

Any User Interface Changes (namelist or namelist defaults changes)? Entires added to namelist defaults.

Does this create a need to change or add documentation? Did you do so? No and no.

Testing performed, if any:
Successfully completed a 1 day test using create_newcase set to grid ne0POLARCAPne30x4_ne0POLARCAPne30x4_mt12 and compset I2000Clm50Sp. No other tests performed.

[wwieder]

Thanks @adamrher. We're in the process of testing and generating new surface datasets again for an upcoming CTSM5.3 tag that will be the final science tag for CESM3 development. Do you need these polar grids for work now, or can we wait to bring them in with the 5.3 series?

Also, I wonder if the tools used to generate this grid should be incorporated into the mksurfdata_esmf workflow?

[ekluzek]

By the grids document we should support: 1979,1850,2000,1979-2026 surface datasets. But, we should separate the mksurfdata_esmf part of this from this part for CTSM support.

[ekluzek]

Things to do here:

• Move this to the b4b-dev branch
• Remove the clm5_1 physics support
• Remove the clm5_0 physics support
• Add the new grid to the build-namelist tester
• Add some tests for this grid to ctsm_sci
• Move new datasets into CESM inputdata and rimport them
• Make an issue to make these datasets in ctsm5.3.0 -- Make polarcap surface datasets in ctsm5.3.0, remove VR 1850 datasets #2720
• Run aux_clm and ctsm_sci test lists

[ekluzek]

@adamrher I'm thinking we should just support this for clm6_0 with cam7.0. With support for cam6.0 being next in priority. This would mainly be for IC file support, and users can still use other options, they'll just need to figure out what IC file to use.

[ekluzek]

I made a list of things to do with this PR to come in. I'm marking it as approved as this looks done to me in terms of what @adamrher needs to give us.

[adamrher]

By the grids document we should support: 1979,1850,2000,1979-2026 surface datasets.

@ekluzek in hindsight, I don't think we need 1850 support for the VR grids. And I noticed in namelist_defaults_ctsm.xml, that the fsurdat entries for 1850 are set to the 1979 fsurdat file for the ARCTIC,ARCTICGRIS VR grids, e.g.,

<fsurdat hgrid="ne0np4.ARCTIC.ne30x4"     sim_year="1850">
lnd/clm2/surfdata_esmf/ctsm5.2.0/surfdata_ne0np4.ARCTIC.ne30x4_hist_1979_78pfts_c240425.nc</fsurdat>

Which I replicated with the POLARCAP grid in this PR. Should we just modify these entries to sim_year="1979" so they are consistent with the file pointed to?

[ekluzek]

@adamrher thanks for letting us know about not needing 1850. I removed it for the other VR grids in the grids spreadsheet. #2498 gets into supporting these 1979 datasets in a clearer more sustainable way. So we'll leave it like it is here for now.

[ekluzek]

These final settings for fsurdat and flanduse_timeseries are superseded by the files that we've created for ctsm5.3.0 in #2500

[ekluzek]

@adamrher we have new surface dataset files for this grid as part of ctsm5.3.0 here:

/glade/campaign/cesm/cesmdata/inputdata/lnd/clm2/surfdata_esmf/ctsm5.3.0/surfdata_ne0np4.POLARCAP.ne30x4_hist_1979_78pfts_c240908.nc
/glade/campaign/cesm/cesmdata/inputdata/lnd/clm2/surfdata_esmf/ctsm5.3.0/landuse.timeseries_ne0np4.POLARCAP.ne30x4_SSP2-4.5_1979-2026_78pfts_c240908.nc

We haven't tested them though, and won't until I get back to this PR after ctsm5.3.0 is done. I have some important cesm3_0_beta03 work that will need to be before this for next week. But, if you'd like to try it yourself before I get to it, we could talk about how you could do that after ctsm5.3.0 is finished. Let me know next week if you'd like to do that...