High resolution regional simulations

We need a clearer workflow for how users can run high resolution regional cases.

Briefly, Xiulin is wanting to run a high resolution CTSM-FATES case over regions of California with DATM inputs that are archived from a WRF simulation. @lmkueppers and @ckoven is this something you've done previously? Moving forward, encouraged use of nuopc, and thought the following would need to be done:
1. Subset surface data (from NLDAS) to the region of interest, given #1408, I wonder if this will be very straightforward?
2. Create a mesh file, #1735 (the mesh file for nuopc is similar in function to the old domain file for mct, but is created differently).
3. Create a regional case that points to the surface data, mesh, and datm files. You can point to the correct DATM files using the datm.streams.xml file in a nuopc case. This may be easier to set up with a usermods_dir.

Here are the questions that may trip us up.
- Are the existing surface data and datm files at the same resolution as the NLDAS grid?
- How does CLM handle information on soil properties coming from NLDAS (presumably they aren't the same)?
- @negin513 and @adrifoster, can the ./subsetdata script be manually changed to create a mesh and surface dataset from higher resolution base maps (3 or 9 km NLDAS). If so,
- Do we have an appropriate resolution mesh file to subset for this regional case?
- @ckoven , masking out regions within the region may be a little trickier. I'd assume this is done with the surface dataset and mesh files? @ekluzek may have ideas based on how we're creating the sparse grid for nuopc.

I'm sure there are additional considerations I'm not thinking about here, but wanted to move this discussion onto github to avoid confusion