`out_name` of longitude / latitude variables

[larsbuntemeyer]

I think in CMIP6, the names of longitude and latitude coordinates is longitude and latitude if they are so-called auxiliary coordinate variable (e.g., 2D projected coordinates with a grid mapping) but they are called lon / lat if they are normal coordinate variables (e.g., the native coordinates of the grid). Should we also use longitude / latitude (if a grid_mapping is present and those are 2D coordinates) or go back to the CMIP5 standard where CORDEX uses lon / lat for the 2D auxiliary coordinates?

https://github.com/WCRP-CORDEX/cordex-cmip6-cmor-tables/blob/80f7f510266884d372d68de6f4d63ffd68255f18/Tables/CORDEX-CMIP6_grids.json#L117-L136

I don't have a preference, right now we use it like in the original CMIP6_grids table.

@gnikulin @sol1105 do you have a preference?

[larsbuntemeyer]

I renamed now to lon /lat to be consistent with the current archive specs draft (section 6). Keep the issue open for now...

[larsbuntemeyer]

See also https://github.com/PCMDI/cmor/issues/470#issuecomment-482143890

[gnikulin]

In CORDEX-CMIP5 we always used lon / lat even for the regular grids. As already mentioned in https://github.com/PCMDI/cmor/issues/470 the CF conventions use lat and lon throughout its examples, but doesn't define these variable names as a requirement for data with two dimensional coordinates. CMIP6 also doesn't define longitude / latitude as a requirement, it's up to the data provider, although CMOR uses "latitude" and "longitude" for auxiliary coordinates (not "lat" and "lon").

I completely agree to use only lon / lat in CORDEX-CMIP6 for all cases. We can close this issue.

[larsbuntemeyer]

Ok, agreed.