🚀[FEA]: utilities to regrid healda to fcn3 and atlas

[nbren12]

Is this a new feature, an improvement, or a change to existing functionality?

New Feature

How would you describe the priority of this feature request

Medium

Please provide a clear description of problem you would like to solve.

This is relatively straightforward for FCN3/FengWu, etc), but not trivial for atlas because it is sensitive to the SST field (see also #681). @aayushg55 has some utility code for this. Should we add this to the repo? We could also put wire this into the healda object so that the user can request 0.25 deg data and get an initial condition that works with Atlas.

@pzharrington @NickGeneva

[NickGeneva]

I know Atlas has some additional steps that should really just get placed into the model wrapper of Atlas. Since @aayushg55 figured out the steps upstreaming those would be good I think.

For others does the current latlon + output_resolution work for fcn3 / fengwu currently in HealDA? Is there another step needed other than e2grid regridding?
https://github.com/NVIDIA/earth2studio/blob/main/earth2studio/models/da/healda.py#L168

[aayushg55]

For models other than Atlas, simply regridding from the healpix output grid to the 0.25 degree latlon grid si sufficient.

For Atlas, we further need to provide surface pressure, precip, and post-processed sst fields. I have some diagnostic utilities to derive surface pressure from mslp and t2m HealDA outputs, precip usingPrecipitationAFNOv2 on our ouputs, and post-process the sst. Where would be the best place to put these steps?

[NickGeneva]

For the post-process of the SST, this should be up streamed into the Atlas wrapper itself.
GenCast does this to make sure the masking if the same across SSTs from different sources. Should just do this for all models going forward as seems this has huge impact on predictive performance

For something like a diagnostic util that can derive sp form mslp and t2m that should be a derived diagnostic model
https://github.com/NVIDIA/earth2studio/blob/main/earth2studio/models/dx/derived.py