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Each directory at the end of a branch of the tree contains one file per parameter containing with all forecast time steps. The files are named <paramId>_<class>_<stream>_<type>_<levtype>_<shortName>_<year>_<expver>_<gridType>.grib2 and are based on the ecCodes paramId, shortName and gridType and the MARS class, stream, type, levtype used for the current operational output at IFS cy49r1.
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The static sample dataset can be used for making some basic tests using your GRIB decoder to ensure the data can be read correctly. This In particular, testing is encouraged if you use a third-party GRIB decoder, such as wgrib2, which is not based on ecCodes.
If your decoder is based on ecCodes then it will need to use a new ecCodes version which will be made available soonbased on ecCodes then ecCodes version 2.42.0 should be used - see ecCodes version 2.42.0 released. This is available for download from our ecCodes Releases page.
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Note that ecCodes version 2.42.0 comes with a significant reworking of the concepts and lookup related to the paramIds/shortNames/names as well as the keys in the MARS namespace in preparation for the migration to GRIB2. This mechanism is predominantly handled by the WMO tables version, with In particular, ecCodes version 2.42.0 should be used with care and not introduced into any operational processing chain unless it has been fully tested beforehand to ensure that none of the changes impact your production. |
The static sample dataset can be decoded with the current version by versions of ecCodes older than 2.42.0 but some keys, in particular the shortName and paramId, may not be set correctly. However, it is possible use the grib_dump tool to inspect the GRIB headers and here the keys are set to the correct values as far as we are aware.
In general, the static sample dataset is not suitable for initialising an NWP model. Although encoding examples of all parameters at all forecast steps are available, for those parameters on constant pressure levels, for example, only the 1hPa level is provided. However, users that initialise NWP models from ECMWF data should note the change in the way the parameters on soil levels are provided as this may require changes to your code. Instead of having four separate parameters at each soil layer, in GRIB2 there will be one parameter available at each of the four layers (levels).
Changes to
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encoding of parameter paramId, shortName, name and units
Surface fields - levType=sfc
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To retrieve these parameters in GRIB2 from MARS, users will need to use the new paramId and also specify the statistical processing time window using a new MARS keyword - timespan - that is to be introduced.
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