WRF Pre-Processing System Version 4.6.0

http://www2.mmm.ucar.edu/wrf/users/

The WRF Pre-Processing System (WPS) is a collection of Fortran and C programs that provides data used as input to the real.exe program. There are three main programs and a number of auxiliary programs that are part of WPS.

For questions and help to run the program, please see the User’s Guide at http://www2.mmm.ucar.edu/wrf/users/docs/user_guide_v4/contents.html and send email to wrfhelp@ucar.edu.

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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 I/O API

ungrib

1. Decodes Grib Edition 1 and 2 data
2. Uses tables to decide which variables to extract
3. Supports isobaric and generalized vertical coordinates
4. Output is in a non-WRF-I/O-API form, referred to as an intermediate format

metgrid

1. Ingest static data and raw meteorological fields
2. Horizontally interpolate meteorological fields to the model domain
3. Output conforms to WRF I/O 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 build mechanism, ./configure ./compile 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 GRIB2” 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.

The utility plotting programs requiring NCAR Graphics are not compiled automatically. Library paths must be set correctly in configure.wps and then compiled using ./compile plotfmt ./compile plotgrids

Building WPS with CMake

The WPS cmake build follows the same procedure as the WRF build procedure, using the following: ./configure_new ./compile_new

The prompts will look similar and present the user with available options specific to their system.

Running WPS (for serially compiled code)

geogrid.exe

• edit namelist.wps (&share and &geogrid sections)
• make sure the correct GEOGRID.TBL is used (ls -l geogrid/GEOGRID.TBL*)
• type ‘geogrid.exe’ to run
• check output in geogrid.log

ungrib.exe

• edit namelist.wps for start_date and end_date, output file prefix (&share and &ungrib sections)
• link correct Vtable: ls -l ungrib/Variable_Tables For example, for NCEP GFS (or AVN, FNL) data, ln -sf ungrib/Variable_Tables/Vtable.GFS Vtable
• link grib data files: link_grib.csh /data-directory/file*
• type ‘ungrib.exe >& ungrib.out’ to run
• check output in ungrib.log and ungrib.out

metgrid.exe

• edit namelist.wps (&share and &metgrid sections)
• make sure the correct METGRID.TBL is used (ls -l metgrid/METGRID.TBL*)
• type ‘metgrid.exe’ to run
• check output in metgrid.log

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

calc_ecmwf_p.exe

purpose: when using ECMWF model data in GRIB format, computes the 3-d pressure, height, and RH fields from the output of ungrib.exe, and writes these fields to a new set of intermediate files to be used in addition to those produced by ungrib. All times between the start_date and end_date specified in the &share namelist will be processed.

usage: calc_ecmwf_p.exe

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://www2.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://www2.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://www2.mmm.ucar.edu/wrf/users/download/get_source.html.