WRF ARW User's Guide - MMM - UCAR

WPS
The data flow between the programs of the WPS is shown in the figure above. Each of
the WPS programs reads parameters from a common namelist file, as shown in the figure.
This namelist file has separate namelist records for each of the programs and a shared
namelist record, which defines parameters that are used by more than one WPS program.
Not shown in the figure are additional table files that are used by individual programs.
These tables provide additional control over the programs’ operation, though they
generally do not need to be changed by the user. The GEOGRID.TBL, METGRID.TBL,
and Vtable files are explained later in this document, though for now, the user need not
be concerned with them.
The build mechanism for the WPS, which is very similar to the build mechanism used by
the WRF model, provides options for compiling the WPS on a variety of platforms.
When MPICH libraries and suitable compilers are available, the metgrid and geogrid
programs may be compiled for distributed memory execution, which allows large model
domains to be processed in less time. The work performed by the ungrib program is not
amenable to parallelization, so ungrib may only be run on a single processor.
Function of Each WPS Program
The WPS consists of three independent programs: geogrid, ungrib, and metgrid. Also
included in the WPS are several utility programs, which are described in the section on
utility programs. A brief description of each of the three main programs is given below,
with further details presented in subsequent sections.
Program geogrid
The purpose of geogrid is to define the simulation domains, and interpolate various
terrestrial data sets to the model grids. The simulation domains are defined using
WRF-ARW V3: User’s Guide 3-2