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(RESOLVED) ungrib does not understand projections of ICON model data

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I am trying to process ICON global model data with the WPS. I selected global 700 hPa temperature field for a specific date ( The data are in grib2 format. However, ungrib.exe complains that the data are in unknown Projection, because the ICON is using unstructured mesh:

*** Starting program ungrib.exe ***
Start_date = 2019-07-19_00:00:00 , End_date = 2019-07-19_00:00:00
output format is WPS
Path to intermediate files is ./
GRIB2 Unknown Projection: 101
ungrib understands projections 0, 20, 30, and 40
STOP Stop in rd_grib2

Please, look also into the attached files.

Best regards,


  • icon_T700.tar.gz
    4.5 MB · Views: 54
  • Vtable.txt
    2.8 KB · Views: 70
  • namelist.wps.txt
    1.6 KB · Views: 67
Unfortunately the ungrib program is specific about the type of projection it expects. For global data sets, either a Gaussian or cylindrical equidistant projection must be used, and for regional data sets, either a Mercator, Lambert conformal, polar stereographic, or cylindrical equidistant may be used. If your data are not on one of the correct grids, then you won't be able to use it with the ungrib program.
Thanks a lot for your response! Could you suggest any tool for interpolating an unstructured mesh (ICON model mesh) to regular lat-lon grid which will be acceptable for the ungrib program?
There are two aspects to this. The first part -- regridding the native ICON data -- can be done using the ESMF regridding utilities, for which there is an NCL interface. DKRZ have a nice document that gives an example of remapping ICON data. Once you've remapped the data onto one of the supported input projections, you'll need to write the data to a format that is usable by the WPS. Rather than writing the data to GRIB format (which is the only file format the ungrib program can read), it may be better to write the remapped ICON data directly to the "intermediate format", which is described in Chapter 3 of the ARW User's Guide.