Describe the Enhancement

This enhancement request arose via GitHub discussions:
dtcenter/METplus#1416

MET versions 10.0.0 and 10.1.0 are not able to read CF-compliant NetCDF files from:
https://www.nohrsc.noaa.gov/snowfall_v2/

Attempting to plot this data with plot_data_plane results in this error:

plot_data_plane sfav2_CONUS_24h_2022020718.nc plot.ps 'name="Data"; level="(*,*)"; file_type=NETCDF_NCCF;'
...
ERROR  : 
ERROR  : NcCfFile::get_grid_from_grid_mapping() -> Cannot extract grid mapping variable ((nul)) from netCDF file.
ERROR  : 

The underlying problem is that the variable attributes are specified as NetCDF strings instead of character arrays. This task to enhance MET's vx_data2d_nccf library (or vx_nc_util) to handle the use of these strings.

For example, the "string" in front of units and stardard_name prevents MET from parsing these attributes:

	double lat(lat) ;
		string lat:long_name = "latitude" ;
		string lat:units = "degrees_north" ;
		string lat:standard_name = "latitude" ;
		lat:resolution = 0.04 ;
		lat:origin_offset = 0.02 ;
		string lat:bounds = "lat_bounds" ;

To test, I used ncdump/ncgen to strip out the "string" settings and re-ran plot_data_plane:
sfav2_CONUS_6h_2022020718.nc.gz

ncdump sfav2_CONUS_6h_2022020718.nc | sed 's/string //g' > sfav2_CONUS_6h_2022020718.ncdump
ncgen -o sfav2_CONUS_6h_2022020718-char.nc sfav2_CONUS_6h_2022020718.ncdump
plot_data_plane sfav2_CONUS_6h_2022020718-char.nc plot.ps 'name="Data"; level="(*,*)";'

Creates this plot:

While I see that the "Data" variable does include some timing information, it is not encoded in a CF-compliant way. If you have any control over the creation of this data, I'd recommend following the conventions for the "Time Coordinate".

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2771021

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