GRIB (GRIdded Binary or General Regularly-distributed Information in Binary form) is a common data format used in meteorology and standardised by the World Meteorological Organisation.

There are two versions of GRIB, GRIB edition 1 (GRIB1) and edition 2 (GRIB2). CEMS-Flood data is available in GRIB2. Further information on the data format is available in the What are GRIB files page.

CEMS-Flood data is archived in the Meteorological Archival and Retrieval System (MARS) at ECMWF in GRIB2 format. Further information on the MARS archive can be found in the MARS user documentation.

There are 2 principal ways to work with GRIB2 files:

• eccodes:  a library developed at ECMWF consisting of a set of tools to code and decode GRIBs, among other formats. The eccodes command-line utilities are commonly used by the meteorology community. Please consult the page How to read GRIB files for an overview of the commands available.
• CFGRIB: a Python interface to the eccodes library. It is one of the supported backend of Xarray.  Please consult the Open CEMS-Flood data page for examples.