Passing user defined variables to a POD

[aradhakrishnanGFDL]

How do we pass user-defined variables to a POD? There were a couple of suggestions from today's mini-leads meeting. Opening this issue to document the potential ways of doing this through environment vars and/or settings.json variables.

This is particularly helpful for Young-Oh's western boundary currents POD.

[aradhakrishnanGFDL]

@bitterbark @jtmims thanks in advance

[wrongkindofdoctor]

@aradhakrishnanGFDL @bitterbark @jtmims

User-defined environment variables are specified in the POD settings file in the POD_ENV_VARS section. POD environment variables can be adjusted by modifying the POD settings file before each mdtf run by the user and/or defining interactive widgets in PODs written as iPython notebooks. POD documentation should include descriptions of any environment variables and acceptable values regardless of format.

The MDSL POD settings file contains pod environment variables for specific supported model datasets, regridding options, regions, and resolution.

[aradhakrishnanGFDL]

@jongsooshin5 Tagging as requested

[bitterbark]

I think the ideal here is that POD env variables are defined in the POD settings file with a default value, and then there could be a way to override defaults when MDTF is called (either from the command line or the input file).

I understand that right now, the values set in the POD settings file will override anything (even set in the user's environment), so at least we can change them somehow, but it would eventually be useful to change stuff on the fly.

I also understand that env vars might not be the best way to do this; I believe they are in because it was the only way to get information to the original NCL code and I don't believe we should be designing around that!

diagnostics/blocking_neale/settings.jsonc
"pod_env_vars" : {
"MDTF_BLOCKING_OBS" : "True", //both ERA & MERRA for now
"MDTF_BLOCKING_OBS_USE_CASE_YEARS": "False", //if False, must set ERA/MERRA/CAM5 FIRST/LAST-YRS below
"MDTF_BLOCKING_OBS_ERA_FIRSTYR" : 2010,
"MDTF_BLOCKING_OBS_ERA_LASTYR" : 2014,
...