d. Run WRF-Var
CONUS Case Study
In this section, you will
learn how to run WRF-Var using observations and a
first guess from a low-resolution (200 km) CONUS domain (see below).
By this stage you have
successfully created the three input files (first guess, observation and
background error statistics files in the directory $DAT_DIR) required to run WRF-Var.
Also, you have successfully downloaded and compiled the WRF-Var
code. If this is correct, we are ready to learn how to run WRF-Var. If not, then you'll need to return to the WRF-Var Tutorial Page
to complete stages a.
i. The Case
The
data for this case is valid at 00 UTC 2nd January 2007. The first
guess comes from the NCEP global final analysis system (FNL), passed through
the WPS and real programs. The first-guess level 18 potential temperature
field is shown below, illustrating the domain:
Note:
In WRF-Var, various NCL scripts are included in the var/graphics/ncl subdirectory to display results.
ii. Changes required
in wrapper script to run con200 case:
The
following environment variables needs to be set in the so-called wrapper script,
“var/scripts/wrappers/da_run_suite_wrapper_con200.ksh”
EL_DIR Full path of the parent code directory
RFVAR_DIR Full directory
path of wrfvar under $REL_DIR
AT_DIR Full path of data input holding ob, be, rc directories
EGION String representing region under $DAT_DIR
B_DIR Full
path for Observation directory
RC_DIR Full path for “FG” directory
BE_DIR Full path for “background error (BE)” directory
INITIAL_DATE Initial date for running WRF-Var
FINAL_DATE Final date for running WRF-Var
The
following environment variables are optional, with default values shown in
parentheses:
EXPT Experiment ID (expt)
RUN_DIR Full path for run directory ($DAT_DIR/$REGION/expt/test_$NUM_PROC)
FC_DIR Analysis output directory ($DAT_DIR/$REGION/expt/fc)
Note:
Since output is written in $RUN_DIR, the user must ensure that this directory
has proper write permission.
iii. Run WRF-Var
Once you have set the necessary
environment variables in the “da_run_suite_wrapper_con200.ksh” script, you can
run this case by typing
da_run_suite_wrapper_con200.ksh
in
the WRFV3/var/scripts/wrappers subdirectory.
Successful completion of
the WRF-Var job will result in a number of output
diagnostic files in the $RUN_DIR directory. The final analysis file, wrfinput_d01,
will appear under $FC_DIR/2007010200 directory. Various textual diagnostics
output files will be explained in the next section on WRF-Var
Diagnostics. Here, we merely wish to run WRF-Var for
this case.
In order to understand the
role of various important WRF-Var options, try
re-running WRF-Var by changing different namelist options via the wrapper script. As a rule, any
WRF-Var namelist which you
want to change may be set via the wrapper script by setting the environment
variable corresponding to its name (all in upper case letters) preceded by “NL_”.
For example, making WRF-Var convergence criteria more
stringent by reducing the value of “EPS” to, e.g., 0.0001 by setting
"export NL_EPS=0.0001" in your wrapper script. If WRF-Var has not converged by the maximum number of iterations
(NTMAX=200) then you may need to increase the value of NTMAX variable by
setting "export NL_NTMAX=500" in your wrapper script and may like to
run the case again. The last section of this tutorial deals with many such
additional exercises.
Note: You may like to
change the $RUN_DIR environment variable to store results separately for each
run. By setting the option “CLEAN=true” in your wrapper script, you can save
lot of space, as this option removes the contents of the “working” directory.
v. What next?
Having run WRF-Var, you should now spend time looking at some of the
diagnostic output files created by WRF-Var:
Miscellanies:
Trouble Shooting: