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Problem

grib_to_netcdf: Why do I get the error "Wrong number of fields... Try using the -T option"?

Solution

You try to retrieve data from the ECMWF data archive in NetCDF netCDF format but the retrieval fails with this message:

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• you request forecast data in NetCDF netCDF format
• your data request contains overlapping "time"+"step" specifications

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In this example you get two data values at the same validity time 2016-12-01, 15:00.  The NetCDF netCDF format does not support multiple data values at a single time, hence the creation of the output NetCDF netCDF file fails, triggering the error message.

Solution

The solution is:

• Retrieve the data in its native GRIB format, which supports multiple data values at any one validity time.
  Then convert the data from GRIB to NetCDF format using the grib_to_netcdf tool with the -T option.
• Retrieve data for each forecast "time" separately, for example for ERA-Interim:
  • first with time = 00:00 and all required steps
  • then with time = 12:00 and all required steps

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