3DVAR Tutorial
g. Updating lateral
boundary conditions
(06/09/2003)
Before running a
forecast, you must first modify the tendencies within the lateral boundary
condition files to be consistent with the new 3DVAR initial conditions. This section
shows you how.
1. Why is
this necessary?
In the previous
sections you have produced the 3DVAR initial conditions, which you wish to use
to initialize an NWP forecast. As well as the analysis, and a host of other
model-related input files required to run your forecast model, you need a
lateral boundary condition file. If you remember back, these were created in
your preprocessing step (INTERPF for MM5, SI for WRF). The lateral boundary
file contains tendencies consistent with the first guess fields (not the
analysis). Therefore we need to update the boundary conditions to be consistent
with the analysis. This is the purpose of the utility update_bc.
You will notice
the MM5 lateral boundary condition file BDYOUT_DOMAIN1 in your ${DAT_DIR}
directory. We need to update the tendencies in this file to be consistent with
the analysis file DAProg_3DVAR.analysis you recently created in your
${RUN_DIR}/${RUN_ID} directory.
2.
Compilation and Running update_bc
To compile the update_bc
utility, cd to 3dvar/da_3dvar/utl (this directory contains a number of
additional useful utility programs beyond the scope of this tutorial).
Type
make update_bc
Then, edit the
script update_bc.csh to change the three filenames to the following:
IC = Input 3DVAR
analysis computed in a previous step.
BC = Input
BDYOUT_DOMAIN1 file that was supplied with the tutorial (original BCS output by
INTERPF).
New_BC = Output
boundary conditions with tendencies corresponding to new analysis.
To run update_bc,
type
update_bc.csh
3. What
next?
Well, that’s the
end of the tutorial! Well done for getting this far. We hope you found the
experience meaningful and feel you can now run NWP forecasts from 3DVAR
analyses!
Trouble Shooting:
1. Having trouble, ask mesouser.