How to read GRIB files!

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Updated by nik: 13 March 2013


GRIdded Binary is a compressed format for meterological data used since 1985.

Requires software for encoding and decoding


Currently used for ECMWF operational surface and pressure level data.


was introduced for ECMWF operational model level data on 18 May 2011.

Migration from GRIB1 to GRIB2 was necessary because GRIB1 data could only hold 126 model levels.

Number of model levels in the high resolution forecast will be increased from 91 to 137 in June 2013.

Pressure levels will still have GRIB1 but eventually this will also be changed.

"Old" model data will still have GRIB1 format in the archive.

GRIB2 also allows more flexibility and is more complex than GRIB1.

For example.

GRIB1: Lon/lat is in milli-degree
GRIB2: Lon/lat is in micro-degree


To decode GRIB data there are software available from ECMWF.

This software is is the GRIB_API (Application Programming Interface) library.

This software hides the binary layer and uses a key/value approach to access the information.

GRIB1 and GRIB2 uses the same function call.

There are both command line tools, and Fortran90/C/Python interfaces.