Step-by-step guide

Local tables for parameters

A common candidate for local adaptation is the handling of local parameters. The standard parameter descriptions are contained in the files:

name.def
paramId.def
shortName.def
units.def

which are placed in directories:

/usr/local/share/eccodes/definitions/grib[edition]

The parameter descriptions for a given centre are contained in the directories:

/usr/local/share/eccodes/definitions/grib[edition]/localConcepts/[centre:s]

So for example the GRIB edition 2 local parameters for DWD (centre=edzw) are defined in definitions/grib2/localConcepts/edzw and GRIB edition 1 local parameters for SMHI (centre=eswi) are in definitions/grib1/localConcepts/eswi.

The following in an example of the contents for the above files in order to handle ECMWF parameter Geopotential in GRIB edition 1:

#Geopotential
'Geopotential' = {
    table2Version = 128 ;
    indicatorOfParameter = 129 ;
}

#Geopotential
'129' = {
    table2Version = 128 ;
    indicatorOfParameter = 129 ;
}

#Geopotential
'z' = {
    table2Version = 128 ;
    indicatorOfParameter = 129 ;
}

#Geopotential
'm**2 s**-2' = {
    table2Version = 128 ;
    indicatorOfParameter = 129 ;
}

And for GRIB edition 2, the contents of the same files for parameter Potential temperature gradient are:

#Potential temperature gradient
'Potential temperature gradient' = {
    discipline = 192 ;
    parameterCategory = 129 ;
    parameterNumber = 3 ;
}

#Potential temperature gradient
'129003' = {
    discipline = 192 ;
    parameterCategory = 129 ;
    parameterNumber = 3 ;
}

#Potential temperature gradient
'ptgrd' = {
    discipline = 192 ;
    parameterCategory = 129 ;
    parameterNumber = 3 ;
}

#Potential temperature gradient
'K' = {
    discipline = 192 ;
    parameterCategory = 129 ;
    parameterNumber = 3 ;
}

Install and test your changes

ecCodes can be instructed to search for definition files in one or more directory trees with environment variable ECCODES_DEFINITION_PATH. All the site specific files have to be stored in a sub-directory tree similar to the hierarchy of the ecCodes distribution. Then, the site specific directory has to be included first in the search path. For example:

ECCODES_DEFINITION_PATH=/usr/site/eccodes/definitions:/usr/local/share/eccodes/definitions

The tool codes_info will tell you if you are using this environment variable or using the standard location for definitions.

To test the local parameter we added earlier, you can take a GRIB2 sample file and change its paramId:

% grib_set -s centre=ecmf,paramId=129003 samples/GRIB2.tmpl out.grib2

Now check the parameter info in the output file:

% grib_ls -jn parameter out.grib2

Also please study the slides here:  Training course presentation.
And the How-To Article GRIB: Converting edition 1 to 2 (The "Local configuration" section)

Related articles

• Page:
  Creating your own local parameters - ecCodes GRIB FAQ
• Page:
  Creating your own local definitions - ecCodes GRIB FAQ
• Page:
  Memory-based access to definition/sample files (MEMFS) - ecCodes FAQ
• Page:
  How do I know if a GRIB message has a Local Use Section - ecCodes GRIB FAQ
• Page:
  Adding your own local definition - ecCodes BUFR FAQ