Fix MERRA-2 access

[jlmaurer]

This PR updates the calls to the MERRA-2 API, which seem to keep changing...

Description

• updated API calls to the GES DISC
• updated the rest of merra2.py module to reflect the changes in variable types and names
• replaced some outdated NETCDF4 writing and reading routines with calls to xarray

Motivation and Context

MERRA-2 was not working due to recent changes to the API, which involved both a change in the dataset short name and a change in the way variables are accessed. This fix is needed as GMAO is also currently not working, and is used for several unit tests. This PR also replaces GMAO with MERRA-2 for those tests.

How Has This Been Tested?

• all unit tests pass locally

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have added an explanation of what your changes do and why you'd like us to include them.
• I have written new tests for your core changes, as applicable.
• I have successfully ran tests with your changes locally.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[jlmaurer]

@cmarshak I'm getting two unit test failures saying that there is no "foo.json" files in test_weather_model_availability_integration_using_valid_range in test_GUNW.py. Any idea what's up with that?

@bbuzz31 this PR should be ready to check, only test failures are with the missing foo.json.

[cmarshak]

Yes, foo.json does not exist. It's a mocked side-effect of all the calls made in the GUNW workflow.

This test makes sure that the attribute model._valid_range is checked and silently stops for the GUNW workflow. This for the situation of HRRR being called for present SLCs that do not have data available (usually we have a long time-series of GUNWs for which a small set of HRRR is not available).

It appears you swapped out GMAO with MERRA2 for this test.

They have different date ranges:

GMAO:

RAiDER/tools/RAiDER/models/merra2.py

Line 48 in 8f41347

self._valid_range = (dt.datetime(1980, 1, 1), "Present")

MERRA2:

RAiDER/tools/RAiDER/models/gmao.py

Line 32 in 8f41347

self._valid_range = (dt.datetime(2014, 2, 20), "Present")

I am not sure what the differences between these two models are and why you changed the models out in the test. Honestly, you could remove GMAO from the test because I don't think we will use GMAO or MERRA2 for cloud processing. If you or David see this model being used, would be good to update the test accordingly (just pick a secondary date outside the date range of MERRA2 here).

Hope that helps.