Support multidimensional coordinates for bounds and regridding

[tomvothecoder]

Description

• Closes [Bug]: Metadata regridding issues related to multidimensional coords #816

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[codecov]

Codecov Report

❌ Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.94%. Comparing base (baf02ae) to head (36aa432).

Files with missing lines	Patch %	Lines
xcdat/regridder/regrid2.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              main     #820      +/-   ##
===========================================
- Coverage   100.00%   99.94%   -0.06%     
===========================================
  Files           18       18              
  Lines         1989     1999      +10     
===========================================
+ Hits          1989     1998       +9     
- Misses           0        1       +1     

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[tomvothecoder]

Notes

• Add guard for regrid2 since it not supported

[pochedls]

Thanks for pushing this forward @jasonb5! This PR seems to work for the example in #816, but I think it is failing for a related case (curvilinear->rectilinear):

wget https://esgf-node.ornl.gov/thredds/fileServer/css03_data/CMIP6/CMIP/CNRM-CERFACS/CNRM-CM6-1/historical/r1i1p1f2/Amon/tas/gr/v20180917/tas_Amon_CNRM-CM6-1_historical_r1i1p1f2_gr_185001-201412.nc
wget https://esgf-node.ornl.gov/thredds/fileServer/css03_data/CMIP6/CMIP/CNRM-CERFACS/CNRM-CM6-1/historical/r1i1p1f2/SImon/siconc/gn/v20180917/siconc_SImon_CNRM-CM6-1_historical_r1i1p1f2_gn_185001-201412.nc

# %% imports
import xcdat as xc

# %% parameters
fn_source = 'siconc_SImon_CNRM-CM6-1_historical_r1i1p1f2_gn_185001-201412.nc'
fn_target = 'tas_Amon_CNRM-CM6-1_historical_r1i1p1f2_gr_185001-201412.nc'

# %% get source / target grids
ds = xc.open_dataset(fn_source)
ngrid = xc.open_dataset(fn_target)

# %% try regridding with xcdat
dsr = ds.regridder.horizontal('tmp2m', ngrid, tool="xesmf", method="conservative_normed", periodic=True)

KeyError: "No 'X' axis dimension coordinate variables were found in the xarray object. Make sure dimension coordinate variables exist, they are one dimensional, and their CF 'axis' or 'standard_name' attrs are correctly set."

I can get this to work with:

import xesmf as xe

regridder = xe.Regridder(ds, ngrid, "conservative_normed", periodic=True, ignore_degenerate=True)                                            
dsr = regridder(ds)