WRF Pre-Processing System Version 2.2.1 (October 2007)
http://www.mmm.ucar.edu/wrf/users/

The WRF Pre-Processing System (WPS) is a collection of Fortran and C programs
that provides data which are input to the real.exe program. There are three 
main programs and a number of auxillary programs that are part of WPS. Both 
the ARW and NMM dynamical cores in WRF are supported by WPS.

For questions and help to run the program, please see the 
User's Guide at http://www.mmm.ucar.edu/wrf/users/docs/user_guide/contents.html
and send email to wrfhelp@ucar.edu.

===================================================

Main programs: geogrid.exe, ungrib.exe, metgrid.exe

Input to the main programs is through the namelist file "namelist.wps". Each 
main program has an exclusive namelist record (named "geogrid", "ungrib",
or "metgrid", respectively), and the three programs have a group record 
(named "share") that each program reads.

geogrid
-------
1) Defines the model horizontal domain
2) Horizontally interpolates static data to the model domain
3) Output conforms to the WRF IO API

ungrib
------
1) Decodes Grib Edition 1 and 2 data
2) Uses tables to decide which variables to extract
3) Isobaric and generalized vertical coordinates
4) Output is in non WRF-API form, referred to as an
   intermediate format

metgrid
-------
1) Ingest static data and raw met fields
2) Horizontally interpolate met fields to the model domain
3) Output conforms to WRF IO API



Parallelism

The geogrid and metgrid programs may be run as distributed memory parallel 
jobs to reduce the time-to-solution. These two programs use MPI calls
directly, compared to WRF which has an abstraction layer (RSL or RSL_LITE).



Grib Edition 2

The Grib Edition 2 compression requires three libraries external to the WPS 
source code: zlib, png, and jasper. It is recommended that users request 
support from their system administrators when installing these packages. Users
can compile the code without these libraries by selecting the "no GRIB2" 
options in the build.



Building WPS

Similar to the WRF package, WPS uses a two-step:
./configure
./compile
build mechanism, which directs the unix make underneath. If the user is on a 
recognized architecture, the configure script will display a list of available
compile options (usually serial vs parallel, Grib 2 enabled vs a "no Grib 2" 
option). For some OS options, there are multiple compilers that are supported.

The configure option lists both "build Grib2" and "do not build Grib2" options.
It is suggested that the first builds be without the Grib Edition 2 capability.

There are a number of utility programs that will be built in WPS/util/ 
directory:

avg_tsfc.exe
------------
purpose: computes a daily mean of the surface air temperature, reads the 
namelist.wps file

usage:
./avg_tsfc.exe


g1print.exe
-----------
purpose: read a Grib Edition 1 file, output information to build a Vtable

usage:
./g1print.exe GRIB1_file


g2print.exe
-----------
purpose: read a Grib Edition 2 file, output information to build a Vtable

usage:
./g2print.exe GRIB2_file


mod_levs.exe
------------
purpose: reduce levels in a intermediate file so that different Grib sources 
may be used for the initial and lateral boundary time periods

usage:
./mod_levs.exe OLD_intermetdiate:date_string \
               NEW_intermetdiate:date_string
Processes a single file at a time, uses the pressure levels defined in the 
namelist.wps file.


plotfmt.exe
-----------
purpose: generate NCAR Graphics metacode 2d horizontal plots of each field 
and level in the intermediate file

usage:
./plotfmt.exe intermediate_file:date_string


plotgrids.exe
-------------
purpose: generate an NCEAR Graphics metacode plot of the domain locations, 
one frame with all of the domain locations plotted, reads the namelist.wps 
file to get the domain information

usage:
./plotgrids.exe


rd_intermediate.exe
-------------------
purpose: read an intermediate file and print the information to the screen

usage:
./rd_intermediate.exe intermediate_file:date_string



Static Input Data

The static input data is provided in two tar files: one contains full 
resolution data (30", 2', 5' and 10') and the other contains only 10' low 
resolution data. The data may be downloaded from 
http://www.mmm.ucar.edu/wrf/users/download/get_source.html.



Meteorological Input Data

The meteorological input data for WPS is the Grib Edition 1 GFS data from NCEP.
A test data set (Jan 2000, 24/12Z to 25/12Z) is available from 
http://www.mmm.ucar.edu/wrf/users/download/get_source.html.



Sample WPS output data for WRF

Samples of the output data from WPS for use in WRF for the Jan 2000 and 
June 2001 cases are provided from
http://www.mmm.ucar.edu/wrf/users/download/get_source.html.
