Feature 1954 semilatlon

[JohnHalleyGotway]

Expected Differences

I feel good about these changes. However, the specification of lat or lon vs TIME is not well tested. The time array is defined as unixtime (number of seconds since Jan 1, 1970). I suspect we'll want to define time in a more user-friendly way. But I'll wait for @CPKalb to test and provide more direction on that.

If changes are needed, recommend we do them with a separate issue in the beta4 development cycle.

• Do these changes introduce new tools, command line arguments, or configuration file options? [No]
  
  If yes, please describe:
  

• Do these changes modify the structure of existing or add new output data types (e.g. statistic line types or NetCDF variables)? [Yes]
  
  If yes, please describe:
  
  Very, very small change. Calling common library code causes the addition of the following NetCDF attribute to the f_super.nc and o_super.nc files created by multivariate MODE:

> 		:MET_tool = "mode" ;

Pull Request Testing

• Describe testing already performed for these changes:
  
  Manually tested many times with plot_data_plane using a python embedding script. Ran it through pcp_combine and grid_stat and confirmed that MET can write this semilatlon data. Also, read the semilatlon NetCDF output of pcp_combine back into other MET tools and confirmed that they can read this data from MET NC files or from Python embedding.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  

  • Review the code changes.
  • Review the newly generated output from the unit tests.
  • Review the documentation updates. Are any more needed?

You can fine the code for this PR compiled in seneca:/d1/projects/MET/MET_pull_requests/met-11.0.0/met-11.0.0-beta3/feature_1954 as the met_test user. Feel free to test there as you see fit.

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]

• Do these changes include sufficient testing updates? [Yes]

• Will this PR result in changes to the test suite? [Yes]
  
  If yes, describe the new output and/or changes to the existing output:
  
  Modifies 2 multivariate MODE NetCDF output files, as noted above. Adds 3 new output files to demonstrate this new functionality:

ERROR: folder /data/output/met_test_truth missing 3 files
    python/wrfout_d01_2008-08-08_12_00_00_PLEV_MERIDIONAL_MEAN.nc 
    python/wrfout_d01_2008-08-08_12_00_00_PLEV_MERIDIONAL_MEAN.ps 
    python/wrfout_d01_2008-08-08_12_00_00_PLEV_ZONAL_MEAN.ps 

• Please complete this pull request review by [Mon 9/19/22].
  

Pull Request Checklist

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• Complete the PR definition above.
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  Select: Reviewer(s)
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[j-opatz]

I think I know the answer, but just clarifying: when it's stated "Two Semi Lat/Lon grids are equal when their lats, lons, levels, and times arrays match.", that means the values of the arrays match, correct? Didn't want the confusion of "equal" meaning lengths of the arrays match.

[JohnHalleyGotway]

That's correct, the code checks that the arrays have the same length and all the array values match.

[j-opatz]

I checked the documentation updates and provided my feedback. Looks like the branch is compiling as expected. The proposed new support is great, but I don't have the data/time to tear into all of this. Hopefully @CPKalb can provide cover on that front.

[JohnHalleyGotway]

Proceeding with the merge for this PR now based on the review from @j-opatz last week.

Recommend that @CPKalb test out this newly added functionality during the MET-11.0.0-beta4 cycle.