Using the grib_api tools

You will find some example data in $SCRATCH/ectrain/trx/openifs or you can use output from one of your own experiments.  Let's play !

Getting help with the tools

Running any of the GRIB API tools without options or input files will produce a UNIX 'man page' style output describing the usage.  Try:

grib_ls

Listing the contents of GRIB files

An inventory of the contents of GRIB files can be obtained with the grib_ls command.

1. For a single file, try:

   grib_ls ICMGGepc8+000000

2. Multiple files:

   grib_ls ICMGG*

3. Counting the number of messages in a file

   grib_count ICMGGepc8+000000

Customising the output of grib_ls

1. Specifying the information to display:

   grib_ls -p dataDate,dataTime,stepRange,shortName,typeOfLevel,level ICMGGepc8+000000

2. Specifying the type of key (s: string, i: integer).  To output the centre as a string (default):

   grib_ls -p centre:s ICMGGepc8+000000

   or as an integer:

   grib_ls -p centre:i ICMGGepc8+000000

3. Listing specific namespace information.  Try:

   grib_ls -n parameter ICMGGepc8+000000

   and

   grib_ls -n statistics ICMGGepc8+000000

   Other namespaces to try are time, vertical and geography.

4. Order the output.  Try:

   grib_ls -B "level desc" ICMSHepc8+000000

   Compare and contrast with:

   grib_ls -B "level:i desc" ICMSHepc8+000000

5. The where option:  IS

   grib_ls -w shortName=stl1 ICMGGepc8+000000

   IS NOT

   grib_ls -w shortName!=stl1 ICMGGepc8+000000

   OR

   grib_ls -w shortName=stl1/z ICMGGepc8+000000

   AND

   grib_ls -w shortName=q,level=10 ICMGGepc8+000000

6. Specifying the step unit.  Compare the output from:

   grib_ls -n time ICMGGepc8+000000

   and

   grib_ls -s stepUnits=m -n time ICMGGepc8+000012

   The stepUnits can be set to s,m,h,3h,6h,12h,D,M,Y,10Y,30Y or C.  The result must be expressible as an integer (try setting stepUnits=D above). This is a temporary change for display purposes only !

    

Obtaining detailed information about a GRIB message with grib_dump

1. To print all of the keys available for a particular GRIB message:

   grib_dump -w shortName=stl1 ICMGGepc8+000012

2. To obtain a listing which is more like the WMO tables:

   grib_dump -O -w shortName=stl1 ICMGGepc8+000012

3. To obtain more detail:

   grib_dump -OatH -w shortName=stl1 ICMGGepc8+000012

Resources and further reading

1. The WMO FM 92 GRIB Manuals can be obtained from www.wmo.int/pages/prog/www/WMOCodes.html
2. The ECMWF GRIB API manual is available at https://software.ecmwf.int/wiki/display/GRIB/Home
3. ECMWF parameter database: http://old.ecmwf.int/publications/manuals/d/gribapi/param
4. GRIB 1 keys http://old.ecmwf.int/publications/manuals/d/gribapi/fm92/grib1/
5. GRIB 2 keys http://old.ecmwf.int/publications/manuals/d/gribapi/fm92/grib2/
6. Edition independent keys http://old.ecmwf.int/publications/manuals/d/gribapi/keys/ 
7. The GRIB API Tools are documented at GRIB tools
8. Details of the GRIB API Fortran 90 interface:Fortran package grib_api
9. Example Python scripts and Fortran 90 and C programs can be found at GRIB API examples
10. ECMWF GRIB API training course material: GRIB API: Library and Tools