Check for THM USE_THETA_M attribute

[braczka]

Description:

Mandate in WRF-DART that if THM variable is present in &model_nml it must be ' perturbed dry adiabatic potential temperature'. This is set through USE_THETA_M option in WRF &dynamics namelist.

Fixes issue

Fixes #837

Types of changes

• 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)
• Documentation update

Documentation changes needed?

None required.

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed

[braczka]

Tested this code using USE_THETA_M = 0 and USE_THETA_M = 1 and gives the expected behavior. /glade/work/bmraczka/DART/models/wrf/MattW_bug/perfect_model_obs

Current WRF 4 and older WRF 3 wrfinput_d01 versions all contain USE_THETA_M as a global attribute, thus no need to set default value behavior in this DART issue. @hkershaw-brown please give this a check, but I think it is ready to go. Please include in the next release, as this problem is not really detectable in practice, and not documented well within WRF unless we mandate exact configuration of THM here within DART.