CDO

Hi,

I'm trying to use CDO to calculate some regional averages of sea ice. The data is provided by NSDIC in the US (https://nsidc.org/data/nsidc-0079/versions/3). I've attached an example dataset from the southern ocean.

I have two versions of CDO: 2.4.0 provided by homebrew on the Mac, which I just discovered doesn't include proj4 support:

Features: 32GB 10threads c++20 Fortran pthreads HDF5 NC4/HDF5 OPeNDAP sz

and 2.1.1 in a python's condo environment, which does:

Features: 32GB 10threads c++17 OpenMP45 Fortran pthreads HDF5 NC4/HDF5/threadsafe OPeNDAP udunits2 proj xml2 magics curl fftw3

Below I'm only using v2.1.1 given the other version doesn't have proj4 support.

This data comes on a polar_stereographic projection which I believe CDO should be able to deal with:

cdo griddes testdata.nc
#
# gridID 1
#
gridtype  = projection
gridsize  = 104912
xsize     = 316
ysize     = 332
xname     = x
xlongname = "x" 
xunits    = "meters" 
yname     = y
ylongname = "y" 
yunits    = "meters" 
xfirst    = -3937500
xinc      = 25000
yfirst    = 4337500
yinc      = -25000
grid_mapping = crs
grid_mapping_name = polar_stereographic
crs_wkt = 'PROJCS["NSIDC Sea Ice Polar Stereographic South",GEOGCS["Unspecified datum  based upon the Hughes 1980 ellipsoid",DATUM["Not_specified_based_on_Hughes_1980_ellipsoid", SPHEROID["Hughes 1980",6378273,298.279411123061,AUTHORITY["EPSG","7058"]], AUTHORITY["EPSG","6054"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]], UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4054"]], PROJECTION["Polar_Stereographic"],PARAMETER["latitude_of_origin",70], PARAMETER["central_meridian",0],PARAMETER["scale_factor",1],PARAMETER["false_easting",0], PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]], AXIS["X",EAST],AXIS["Y",NORTH],AUTHORITY["EPSG","3412"]]'
long_name = "NSIDC_SH_PolarStereo_25km" 
standard_parallel = -70.
inverse_flattening = 298.279411123064
proj4text = "+proj=stere +lat_0=-90 +lat_ts=-70 +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378273  +b=6356889.449 +units=m +no_defs" 
straight_vertical_longitude_from_pole = 0.
false_easting = 0.
false_northing = 0.
semi_major_axis = 6378273.
latitude_of_projection_origin = -90.
GeoTransform = "-3950000 25000 0 4350000 0 -25000" 
longitude_of_prime_meridian = 0.
srid = "urn:ogc:def:crs:EPSG::3412" 
cdo    griddes: Processed 1 variable [0.04s 15MB]

I can average the entire sea ice field using fldmean just fine, but trying, say, to select a box fails:

cdo -sellonlatbox,-90,-70,-68,-65 -selname,F17_ICECON testdata.nc test.nc

Now, I noticed that this file contains a 'proj4text' attribute, not the 'proj4_params' as suggested in CDO's documentation, so I updated this using the setgrid command. I've attached the resulting testdata2.nc and grid.txt file I used. However, this doesn't solve the problem.

I'm sure I'm missing something glaringly obvious, but any ideas of what's going on here?

Thanks!