WRF ARW User's Guide - MMM - UCAR

&share
wrf_core = 'ARW',
max_dom = 2,
start_date = '2008-03-24_12:00:00','2008-03-24_12:00:00',
end_date = '2008-03-24_18:00:00','2008-03-24_12:00:00',
interval_seconds = 21600,
io_form_geogrid = 2
/
&geogrid
parent_id = 1, 1,
parent_grid_ratio = 1, 3,
i_parent_start = 1, 31,
j_parent_start = 1, 17,
s_we = 1, 1,
e_we = 74, 112,
s_sn = 1, 1,
e_sn = 61, 97,
geog_data_res = '10m','2m',
dx = 30000,
dy = 30000,
map_proj = 'lambert',
ref_lat = 34.83,
ref_lon = -81.03,
truelat1 = 30.0,
truelat2 = 60.0,
stand_lon = -98.
geog_data_path = '/mmm/users/wrfhelp/WPS_GEOG/'
/
The namelist variables that are affected by nests are shown in the (partial) namelist
records above. The example shows namelist variables for a two-domain run (the coarse
domain plus a single nest), and the effect on the namelist variables generalize to multiple
nests in the obvious way: rather than specifying lists of two values, lists of N values must
be specified, where N is the total number of model grids.
WPS
In the above example, the first change to the “share” namelist record is to the max_dom
variable, which must be set to the total number of nests in the simulation, including the
coarse domain. Having determined the number of nests, all of the other affected namelist
variables must be given a list of N values, one for each grid. The only other change to the
“share” namelist record is to the starting and ending times. Here, a starting and ending
time must be given for each nest, with the restriction that a nest cannot begin before its
parent domain or end after its parent domain; also, it is suggested that nests be given
starting and ending times that are identical to the desired starting times of the nest when
running WPS. This is because the nests get their lateral boundary conditions from their
parent domain, and thus, only the initial time for a nest needs to be processed by WPS,
except when grid nudging, also called analysis nudging, is used in WRF. It is important
to note that, when running WRF, the actual starting and ending times for all nests must be
given in the WRF namelist.input file.
The remaining changes are to the “geogrid” namelist record. In this record, the parent of
each nest must be specified with the parent_id variable. Every nest must be a child of
exactly one other nest, with the coarse domain being its own parent. Related to the
identity of a nest's parent is the nest refinement ratio with respect to its parent, which is
WRF-ARW V3: User’s Guide 3-19