Using gdal.Warp() on netCDF file. Simple case fails

Question

I'm using the python API to GDAL to try to do a simple geographic warp of a netCDF4 satellite file to a small sub region. My python program fails to produce any output but does not throw any exceptions or errors. Any ideas?

The command line operation of gdalwarp works fine and produces meaningful netCDF output (for a single band or variable). But the python version does not. THe output 'ds' is "None' and no netCDF output file is created. Here is a snapshot:

    from osgeo import gdal, gdalconst


kwargs = {'format': 'netCDF', 'copyMetadata': True, 
          'outputBounds': '[-29 -2 -25 2]', 
          'dstSRS':'+proj=longlat +datum=WGS84 +no_defs'
         }
          

src_filename = './subset_20180729030000-JPL-L2P_GHRSST-SSTskin-MODIS_A-N-v02.0-fv01.0.nc'
nc_file = 'NETCDF:' + src_filename
src = gdal.Open(nc_file, gdalconst.GA_ReadOnly)

subDatasets = src.GetSubDatasets()
#print('subsdatatsets', subDatasets)

ds = gdal.Warp('./output_lonlat.nc', src, **kwargs)
print("ds is ", ds)

del ds

Here is the command line operation that does work:

% gdalwarp -t_srs "+proj=longlat +datum=WGS84 +no_defs" -te -29 -2 -25 2 NETCDF:"./subset_20180729030000-JPL-L2P_GHRSST-SSTskin-MODIS_A-N-v02.0-fv01.0.nc":sea_surface_temperature -overwrite -of netCDF out_lonlat.nc

Answer 1

I found the solution:

• I was using the arguments to outputBounds wrong. Its just an array and not a string.
• As @user30184 suggested and I previously suspected gdal.Warp() only works on one netCDF layer (variable) at a time. To work on multiple variables you would need to read and execute on them one at a time.

Here is code that executes correctly:

        from osgeo import gdal, gdalconst
    
    
    kwargs = {'format': 'netCDF', 'copyMetadata': True, 
               'outputBounds': [-29, -2, -25, 2], 
              'dstSRS':'+proj=longlat +datum=WGS84 +no_defs',
             }
        
    # Source netCDF file
    src_filename = './subset_20180729030000-JPL-L2P_GHRSST-SSTskin-MODIS_A-N-v02.0-fv01.0.nc'
    
    # load the sea_surface_temperature variable
    nc_file = 'NETCDF:' + src_filename + ':sea_surface_temperature'
    src = gdal.Open(nc_file, gdalconst.GA_ReadOnly)
    
    # perform the warp and resample
    ds = gdal.Warp('./output_lonlat.nc', src, **kwargs)
    del ds