Add earth-relative rotation of U10/V10 fields

[lpilz]

Change Summary

Adds rotation of U10/V10 wind fields like U/V.

Related issue number

Closes #112

Checklist

• [x] Unit tests for the changes exist
• [x] Tests pass on CI
• [x] Documentation reflects the changes where applicable

[lpilz]

Wasn't quite sure if there is a standard_name for earth-relative 10m winds, which I just couldn't find but I guess it doesn't exist.

[jthielen]

Wasn't quite sure if there is a standard_name for earth-relative 10m winds, which I just couldn't find but I guess it doesn't exist.

Yeah, I haven't found a good consensus for handling these, so I've usually just skipped the standard name (like done here). If it were to be implemented, the possibilities I'd see are:

• use the same eastward_wind style standard name, but with a scalar height auxiliary coordinate set at 10 (with appropriate metadata)
• try to adapt the "Surface" standard name construction guidelines to have something like eastward_wind_at_10_meters_above_ground_level (which would still be provisional, as I haven't seen that style of surface specification used elsewhere)

[lpilz]

Great! Thanks for your insight. I guess, we'll just amend it once these names are actually part of the CF standards...