WRF ARW User's Guide - MMM - UCAR

WRF-VAR
Note: Larger analysis increments indicate a larger data impact in the corresponding region
of the domain.
Updating WRF boundary conditions
Before running NWP forecast using WRF-model with WRF-Var analysis, the values and
tendencies for each of predicted variables for the first time period in the lateral boundary
condition file for domain-1 (wrfbdy_d01) must be updated to be consistent with the new
WRF-Var initial condition (analysis). This is absolutely essential. Moreover, in the cycling
run mode (warm-start), the low boundary in the WRF-Var anaylsis file also need to
be updated based on the information of the wrfinput file generated by WPS/real.exe at the
analysis time. So there are three input files: WRF-Var analysis, wrfinput and wrfbdy files
from WPS/real.exe, and a namelist file: param.in for running da_update_bc.exe for
domain-1.
For the nested domains, domain-2, domain-3…, the lateral boundaries are provided by
their parent domains, so no lateral boundary update needed for these domains, But the
low boundaries in each of the nested domains’ WRF-Var analysis files are still need to be
updated. In these cases, you must set the namelist variable, domain_id > 1 (default is 1
for domain-1), and no wrfbdy_d01file need to be provided to the namelist variable:
wrf_bdy_file.
This procedure is performed by the WRF-Var utility called da_updated_bc.exe.
Note: Make sure that you have da_update_bc.exe in WRFDA/var/build directory. This
executable should be created when you compiled WRF-Var code,
To run da_update_bc.exe, follow the steps below:
> cd WRFDA/var/test/update_bc
WRF-ARW V3: User’s Guide 6-33