issue_comments

I can't seem recreate this with a minimal example, xarray roundtrips a NetCDF file with a coordinates attribute correctly:

```python from netCDF4 import Dataset import xarray as xr

with Dataset('test.nc', format='NETCDF4', mode='w') as nc: nc.createDimension('dim1', size=0) var = nc.createVariable('var1', 'f8', dimensions=('dim1')) var[:] = [1., 2., 3.] var.setncattr('coordinates', 'dim1')

xr.open_dataset('test.nc').to_netcdf('test2.nc') ```

There is something peculiar about how WRF handles the coordinates attribute, but I can't see anything off about it yet.

Interestingly, I can workaround the WRF coordinates issue by setting decode_coords=False in xarray.open_dataset(), for example, this works:

python xr.open_dataset('wrfout_d01_2019-04-16_15_00_00', decode_coords=False).to_netcdf('test.nc')

while this doesn't:

python xr.open_dataset('wrfout_d01_2019-04-16_15_00_00').to_netcdf('test.nc')

I ran into this issue trying to roundtrip a WRF output file. It looks like xarray raises an error for any NetCDF file that has variables with a coordinates attribute:

python # These coordinates are saved according to CF conventions for var_name, coord_names in variable_coordinates.items(): attrs = variables[var_name].attrs if 'coordinates' in attrs: raise ValueError('cannot serialize coordinates because variable ' "%s already has an attribute 'coordinates'" % var_name) attrs['coordinates'] = ' '.join(map(str, coord_names))

~~Both this choice, and the proposed solution in this issue (delete all coordinates attributes), I don't understand.~~ Variables with a coordinates attribute are CF conforming, so xarray should be able to play along with this.

~~The solution that makes more sense to me is to raise a warning and overwrite or ignore the coordinates attribute, if the attribute is already present. Later step of the fix could even be a keyword argument to allow the user to choose whether to overwrite or ignore "conflicting" attributes.~~

Or perhaps I'm missing something obvious here... Let me know either way. I'd be happy to make a PR to patch this.

That's perfect. Thank you!

Hello, I realized I never followed up with this but am again running into issues. The real problem for me is that deleting coordinates on 30+ variables isn't really feasible. Is it possible to delete the coordinates attribute for all variables?

Thanks for the solution (that was my SO post as well). Deleting the attrs.['coordinates'] was a clean workaround. Here's the requested WRF meta. It was concatenated with NCO, but meta should be consistent.

WRF_meta.txt

Did you ever find a solution to this?