Concatenate datasets when some variables are present in one dataset and not present in other dataset

[andersy005]

Currently, xarray.concat() doesn't know how to deal with datasets for which one dataset contains some variables and these same variables are not present in the rest of the datasets to concatenate.

To address this issue, there are two options:

• Add NaNs by determining the set of variables that are not in all datasets but at least in one dataset
  and use .full_like(..., fill_value=np.nan) to add the variables not present in the other dataset (
• Dropping the problematic variables
  Either option would probably need to be done prior calling xr.concat() in join_new() and join_existing() introduced in Rewrite intake-esm's core based on ESM Collection Specification #135

[dcherian]

Upstream issue: pydata/xarray#508

This would be a relatively easy fix in concat if you're up for it. I'm happy to help.

[andersy005]

Sure. I will try working on this during the CMIp6 hackathon

[dcherian]

See pydata/xarray#3545. It could use some real world testing if you have the time...