Technical Report No. ? - DKRZ

2. OUTLINE OF THE SYSTEMS
DKRZ GRIB/EXTRA Format Module Documentation
A system has been devised involving two standardised data formats and a library of programs which perform
basic arithmetic, statistics or extraction on any dataset that is in one of these formats. The purpose
of the system is to enable users to extract the data they need without having to write programs or do long
complicated data manipulations. These programs also include some complex data analysis routines such
like EOF’s, canonical correlation and spectral analysis.
The two data formats are called EXTRA-Format and GRIB-Format. The EXTRA-Format was designed
by E. Kirk (University of Hamburg). The GRIB-Format was devised by WMO. One set of programs convert
between EXTRA- and GRIB-Format.
2.1 THE GRIB-FORMAT
2.1.1 Outline
The GRIB-Format was devised by WMO for use in weatherforecasting. It is used in Hamburg for model
output data. Its data structure is readable on any computer and also provides a highly dense packaging.
Further details can be found in
WMO-No. 306 Manual on Codes, Volume 1, International Codes, Part B - Binary Codes
2.1.2 The System
The GRIB-Format system comprises a set of program modules.
The GRIB-Format program names are listed in section 3.1 . The method of calling the programs is given
in section 3.2 . An introduction to the GRIB-Format is given in section 3.3 . The details of all the program
modules can be found in section 3.4 . In section 3.5 some examples of program calls are shown.
2.1.3 Method of Use
The user should be familiar with the use of the procedure EXTRACT and with UNIX before using the
GRIB program modules. Use of EXTRACT is described in section 3.4.1 . The user runs the program
modules under UNIX. The procedure EXTRACT itself makes use of the GRIB system, hiding details of
the GRIB-Format to the user.
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