Bugfix: Refine support for coordinate dimensions in CF-compliant NetCDF files

[JohnHalleyGotway]

Describe the Enhancement

This issue arose via GitHub discussion dtcenter/METplus#2273 from @robdarvell and is demonstrated by running the plot_data_plane tool. Use this file to demonstrate the issue:
percentile_extract_20230729T1200Z-B20230725T0030Z-visibility_at_screen_level.nc.gz

The goal is to retrieve 2D fields from this variable:
float visibility_in_air(percentile, projection_y_coordinate, projection_x_coordinate) ;

Plotting the 0-th percentile index works as expected:
plot_data_plane percentile_extract_20230729T1200Z-B20230725T0030Z-visibility_at_screen_level.nc plot.ps 'name="visibility_in_air"; level="(0,*,*)";'

Plotting the VALUE of the first percentile also works fine:
plot_data_plane percentile_extract_20230729T1200Z-B20230725T0030Z-visibility_at_screen_level.nc plot.ps 'name="visibility_in_air"; level="(@5,*,*)";'

However, plotting ANY OTHER index or percentile value produces a runtime error:

• name="visibility_in_air"; level="(1,*,*)";'
• name="visibility_in_air"; level="(@10,*,*)";'
• name="visibility_in_air"; level="(6,*,*)";'
• name="visibility_in_air"; level="(@50,*,*)";'

Here's the error:

ERROR  : 
ERROR  : MetNcCFDataFile::data_plane(VarInfo &, DataPlane &) -> the requested vertical value 50 for "visibility_in_air" variable does not exist (data size = 1).
ERROR  : 

I assumed that the changes for #1815 included in MET version 11.0.0 would enable this logic to work. In general, for an N-dimensional NetCDF variable, exactly 2 of those dimensions should define the X/Y dimensions. The remaining dimensions should be settable by specifying their index as an integer. Additionally, for coordinate variables (i.e. dimension and 1-d variable of the same name), MET should support the @ syntax to specify the value for that dimension.

This issue is to refine the logic to support the processing of this data.

Please fix this in the main_v11.1 branch to be included in an 11.1.1 bugfix release. Please also fix this in the develop branch to be included in the 12.0.0 official release.

Recommend adding a unit test using the input file.

Time Estimate

2 days?

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2799991

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[JohnHalleyGotway]

@hsoh-u, FYI, during the METplus engineering meeting on Tuesday 8/8, the team decided to reclassify this issue as a bug instead of an enhancement. As such, please fix this in the main_v11.1 branch first.

[hsoh-u]

MET picks the "height" variable as the vertical level instead of "percentile" because of the standard name. The "height" variable has only 1 value. This caused problem, only offset 0 works for vertical offset.

MET code sets the coordinate variables by the standard names. The standard names as the coordinate variables are time, latitude, longitude, air_pressure, and height. The solution will be exclude them by looking at the dimensions.

The workaround is removing the standard name and adding the long_name at the "height" variable.

        float percentile(percentile) ;
                percentile:units = "%" ;
                percentile:long_name = "percentile" ;
        float height ;
                height:units = "m" ;
                height:standard_name = "height" ;
                height:positive = "up" ;