I/O: Add standard name metadata to all output variables - Re: CF-Compliance

[AaronDonahue]

We have been talking about making our output CF-Compliant for awhile. I'm adding this Issue so we can track that effort.

My understanding is that we simply need to add the standard_name metadata to a variable to make it CF-Compliant. The trick is that we would want to ensure that every variable has the correct "standard name" according to the CF guidlines, see https://cfconventions.org/Data/cf-standard-names/current/build/cf-standard-name-table.html

Ideas we have considered:

• Add a "standard_name" internal variable to the field class that can be set by add_field
• Have a lookup dictionary available to I/O that will check an EAMxx field name for a predefined standard name.