WRF ARW User's Guide - MMM - UCAR

MODEL
The purpose of this step is to ingest higher resolution terrestrial fields and corresponding
land-water masked soil fields.
Before doing this step, WPS should be run for one coarse and one nest domains (this
helps to line up the nest with the coarse domain), and for the one time period the one-way
nested run is to start. This generates a WPS output file for the nested domain (domain 2):
met_em.d02..
- Rename met_em.d02.* to met.d01.* for the single requested fine-grid start
time. Move the original domain 1 WPS output files before you do this.
- Edit the namelist.input file for fine-grid domain (pay attention to column 1
only) and edit in the correct start time, grid dimensions.
- Run real.exe for this domain. This will produce a wrfinput_d01 file.
- Rename this wrfinput_d01 file to wrfndi_d02.
Step 3: Make the final fine-grid initial and boundary condition files
- Edit namelist.input again, and this time one needs to edit two columns: one for
dimensions of the coarse grid, and one for the fine grid. Note that the boundary
condition frequency (namelist variable interval_seconds) is the time in seconds
between the coarse-grid model output times.
- Run ndown.exe, with inputs from the coarse grid wrfout file(s), and
wrfndi_d02 file generated from Step 2 above. This will produce wrfinput_d02
and wrfbdy_d02 files.
Note that program ndown may be run serially or in MPI, depending on the selected
compile option. The ndown program must be built to support nesting, however. To run
the program, type,
./ndown.exe
or
mpirun –np 4 ./ndown.exe
Step 4: Make the fine-grid WRF run
- Rename wrfinput_d02 and wrfbdy_d02 to wrfinput_d01 and
wrfbdy_d01, respectively.
- Edit namelist.input one more time, and it is now for the fine-grid domain only.
- Run WRF for this grid.
The figure on the next page summarizes the data flow for a one-way nested run using
program ndown.
WRF-ARW V3: User’s Guide 5-15