WRF ARW User's Guide - MMM - UCAR

f. Moving-Nested Run
MODEL
Two types of moving tests are allowed in WRF. In the first option, a user specifies the
nest movement in the namelist. The second option is to move the nest automatically
based on an automatic vortex-following algorithm. This option is designed to follow the
movement of a well-defined tropical cyclone.
To make the specified moving nested run, select the right nesting compile option (option
‘preset moves’). Note that code compiled with this option will not support static nested
runs. To run the model, only the coarse grid input files are required. In this option, the
nest initialization is defined from the coarse grid data - no nest input is used. In addition
to the namelist options applied to a nested run, the following needs to be added to
namelist section &domains:
num_moves: the total number of moves one can make in a model run. A move of any
domain counts against this total. The maximum is currently set to 50, but it can be
changed by change MAX_MOVES in frame/module_driver_constants.F.
move_id: a list of nest IDs, one per move, indicating which domain is to move for a
given move.
move_interval: the number of minutes since the beginning of the run that a move is
supposed to occur. The nest will move on the next time step after the specified instant of
model time has passed.
move_cd_x,move_cd_y: distance in number of grid points and direction of the nest
move(positive numbers indicating moving toward east and north, while negative numbers
indicating moving toward west and south).
Parameter max_moves is set to be 50, but can be modified in source code file
frame/module_driver_constants.F if needed.
To make the automatic moving nested runs, select the ‘vortex-following’ option when
configuring. Again note that this compile would only support auto-moving nest, and will
not support the specified moving nested run or static nested run at the same time. Again,
no nest input is needed. If one wants to use values other than the default ones, add and
edit the following namelist variables in &domains section:
vortex_interval: how often the vortex position is calculated in minutes (default is
15 minutes).
max_vortex_speed: used with vortex_interval to compute the radius of search for
the new vortex center position (default is 40 m/sec).
corral_dist: the distance in number of coarse grid cells that the moving nest is
allowed to come near the coarse grid boundary (default is 8). This parameter can be used
to center the telescoped nests so that all nests are moved together with the storm.
track_level: the pressure level (in Pa) where the vortex is tracked.
WRF-ARW V3: User’s Guide 5-17