ak_ar5_wrf dataset processing

Processing artifacts and aggregation concept is worked up here: https://code.usgs.gov/wma/nhgf/geo-data-portal/thredds-config/-/tree/master/mnt_thredds/ak_ar5_wrf

Files in S3 under here: s3://nhgf-development/thredds/ak_ar5_wrf/

Join strategy involves many ncml join aggregations along time in an ncml folder and a few union aggregations that gather together all the joins.

Closure criteria: migrate this ncml join/union strategy to a one or more zarr datasets as appropriate and plan documentation with @ellenbrown and others as needed.

Please flesh out further useful details and pull me in as needed @kdooley1.