Using ESMF_Regrid

A command line utility to apply ESMF_RegridWeightGen weights to datasets should be added. This will avoid some unnecessay IO that is apparent in these examples. This utility for applying ESMF weights should probably go in xESMF.

ESMF_Regrid example: Sample lat-lon data to C24

# Download sample NetCDF data
wget https://www.unidata.ucar.edu/software/netcdf/examples/sresa1b_ncar_ccsm3-example.nc

# Add "coordinates" attributes to the "tas" variable. ESMF requires this "coordinates" attribute.
ncatted -a coordinates,tas,o,c,"lon lat" sresa1b_ncar_ccsm3-example.nc

# Create C24 gridspec
gridspec-create gcs 24

# Create empty datasets to recieve data to
gridspec-utils touch -m c24_gridspec.nc c24_recv

# Regrid
ESMF_Regrid -s sresa1b_ncar_ccsm3-example.nc -d c24_gridspec.nc --dstdatafile c24_recv --src_var tas --dst_var tas -m conserve

# Join the data tiles
gridspec-utils join c24_recv -m c24_gridspec.nc -d nf -s joinspec.json

where joinspec.json is

{
  "rename_dict": {},
  "transpose": ["time", "nf", "Ydim", "Xdim"]
}

ESMF_Regrid example: Cubed-sphere to lat-lon

# Create output file (for lat-long grids, ESMF_Regrid's output goes to this file)
gridspec-create latlon 180 360
mv regular_lat_lon_180x360.nc my_output_latlon_file.nc

# Split the input cubed-sphere data into 6 separate files
gridspec-utils split -m c24_gridspec.nc -d nf GCHP.SpeciesConc.20180101_1200z.nc4

# Regrid
VARIABLES=SpeciesConc_O3,SpeciesConc_NO,SpeciesConc_NO2,SpeciesConc_HNO3,SpeciesConc_PAN,SpeciesConc_CO,SpeciesConc_CH2O,SpeciesConc_SO2,SpeciesConc_NH3,SpeciesConc_H2O
ESMF_Regrid -s c24_gridspec.nc --srcdatafile GCHP.SpeciesConc.20180101_1200z -d my_output_latlon_file.nc --src_var ${VARIABLES} --dst_var ${VARIABLES} -m conserve