WRF ARW User's Guide - MMM - UCAR

estart file named wrfrst_d_ will be written. The date string
represents the time when the restart file is valid.
MODEL
When one starts the restart run, edit the namelist.input file, so that your start_*
time will be set to the restart time (which is the time the restart file is written). The other
namelist variable one must set is restart, this variable should be set to .true. for a
restart run.
In summary, these namelists should be modified:
start_*, end_*: start and end times for restart model integration
restart: logical to indicate whether the run is a restart or not
Hint: Typically the restart file is a lot bigger in size than the history file, hence one may
find that even it is ok to write a single model history output time to a file in netCDF
format (frame_per_outfile=1), it may fail to write a restart file. This is because
the basic netCDF file support is only 2Gb. There are two solutions to the problem. The
first is to simply set namelist option io_form_restart = 102 (instead of 2), and
this will force the restart file to be written into multiple pieces, one per processor. As long
as one restarts the model using the same number of processors, this option works well
(and one should restart the model with the same number of processors in any case). The
second solution is to recompile the code using the netCDF large file support option (see
section on “Installing WRF” in this chapter).
d. Two-way Nested Runs
A two-way nested run is a run where multiple domains at different grid resolutions are
run simultaneously and communicate with each other: The coarser domain provides
boundary values for the nest, and the nest feeds its calculation back to the coarser
domain. The model can handle multiple domains at the same nest level (no overlapping
nest), and multiple nest levels (telescoping).
When preparing for a nested run, make sure that the code is compiled with basic nest
options (option 1).
Most of options to start a nest run are handled through the namelist. All variables in the
namelist.input file that have multiple columns of entries need to be edited with
caution. Do start with a namelist template. The following are the key namelist variables
to modify:
start_*, end_*: start and end simulation times for the nest
input_from_file: whether a nest requires an input file (e.g. wrfinput_d02). This
is typically used for a real data case, since the nest input file contains nest topography and
land information.
WRF-ARW V3: User’s Guide 5-11