Writing out a siphon'd xarray dataset as a netCDF

[ThomasMGeo]

Hello! I am trying to write out a netCDF file from a siphon'd xarray dataset. Writing out to Zarr works fine. This may be in the wrong spot (see image).

That is the input:

catUrl = "https://thredds.ucar.edu/thredds/catalog/grib/NCEP/GFS/Global_onedeg_ana/catalog.xml";
datasetName = "Full Collection Dataset";

catalog = TDSCatalog(catUrl)

ds2 = catalog.datasets[datasetName].remote_access(use_xarray=True)
print('ds is a:', type(ds2))

and writing it out:

# Write the second dataset (ds2) to NetCDF format and print the output path
ds2.to_netcdf(paths['ds2'])
print(f"Second dataset written to {paths['ds2']} in NetCDF format.")

• Problem description: this should explain why the current behavior is a problem and why
  the expected output is a better solution.

I just wanted to write out a netCDF file, I didn't modify the file to my knowledge. Happier to share a more in depth workflow. The error I get is below:

RuntimeError: NetCDF: Name contains illegal characters

• Which platform
  MacOS, python 3.10
• Versions. Include the output of:

siphon version 0.9

[ThomasMGeo]

Notebook that has more of the workflow: https://github.com/Unidata/MLscratchpad/blob/main/BlogNotebooks/netCDF_vs_Zarr_filestoage.ipynb

[tdrwenski]

I reproduced this and did notice that

print(ds2.dims)

returns

Frozen({'sigma_layer': 4, '': 2, 'pressure_difference_layer': 1, 'pressure_difference_layer1': 1, 'time': 1, 'isobaric': 41, 'lat': 181, 'lon': 360, 'hybrid': 1, 'isobaric1': 22, 'potential_vorticity_surface': 2, 'sigma': 1, 'altitude_above_msl': 3, 'height_above_ground': 2, 'height_above_ground1': 6})

I think possibly the "Name contains illegal characters" could be referring to a dimension of size 2 with an empty name. Not sure why that dimension has no name when reading in with xarray but is not present when reading with Opendap though.