UPP Online Tutorial for UPPV4.1 | Setup and Run > Control File for GRIB1

This section describes the parameter file, which can be modified to control how the post processing is performed, for outputting GRIB1 format available for WRF-ARW only. A default control file for users to practice with can be found in /UPPV4.1/parm/wrf_cntrl.parm for WRF runs.

Components of the WRF control file

The control file is composed of a header and a body. The header specifies the output file information. The body allows you to select which fields and levels to process.

The header of the wrf_cntrl.parm file contains the following variables:

  • KGTYPE: defines the output grid type, which should always be 255
  • IMDLTY: identifies the process ID for AWIPS
  • DATSET: defines the prefix used for the output file name (i.e. WRFPRS for WRF runs)

The body of the wrf_cntrl.parm file is composed of a series of line pairs similar to:

     (PRESS ON MDL SFCS ) SCAL=( 3.0)
     L=(11000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000)

The first line specifies the:

  • variable (e.g. PRESS)
  • level type (e.g. ON MDL SFCS)
  • precision of the data written out to the GRIB1 file (e.g. SCAL=3.0)

The second line specifies the levels on which the variable is to be output. In this example, a "0" indicates no output on this level and a "1" indicates for that variable to be output at the level specified by the position of the digit and the level type defined.

For those wishing to modify the wrf_cntrl.parm file, please refer to How to control which GRIB1 variables and levels are output.