Assimilation of Accumulated Precipitation Data

Reference: Precipitation Data Assimilation in the WRFDA Users' Guide

Source code

Get the pre-compiled code, if you have not done so.

WRFDA/var/build/da_wrfvar.exe_4dvar (this is renamed from da_wrfvar.exe) is the executable that will be used in this 4D-VAR session. Rainfall can only be assimilated with 4D-VAR.

Working directory

We recommend you create a new working directory for this exercise:

mkdir /data1/$USER/DA/rainfall
cd /data1/$USER/DA/rainfall

Input data

The test data for this rainfall tutorial case can be found in /wrfhelp/DATA/WRFDA/Rainfall

ln -fs /wrfhelp/DATA/WRFDA/Rainfall/ob/ob.rain.2008020518.06h ob07.rain
ln -fs /wrfhelp/DATA/WRFDA/Rainfall/rc/wrfinput_d01 ./fg
ln -fs /wrfhelp/DATA/WRFDA/Rainfall/rc/wrfinput_d01 .
ln -fs /wrfhelp/DATA/WRFDA/Rainfall/rc/wrfbdy_d01 .
ln -fs /wrfhelp/DATA/WRFDA/Rainfall/be/be.dat .

These are the observation, first guess, boundary, and background error files, respectively. It is necessary to link a few more files for a 4D-VAR precipitation run

ln -fs /data1/${USER}/DA/WRFDA/run/RRTM_DATA_DBL ./RRTM_DATA
ln -fs /data1/${USER}/DA/WRFDA/run/*.TBL .

Edit namelists

A very basic namelist.input file for running this tutorial case is available at /wrfhelp/DATA/WRFDA/Rainfall/namelist.input.

cp /wrfhelp/DATA/WRFDA/Rainfall/namelist.input .
vi namelist.input

Pay special attention to the following namelist variables, making sure they are set to these values:

&wrfvar1
var4d=true,
var4d_lbc=false,
var4d_bin=3600,
var4d_bin_rain=21600,
...
/
...
&wrfvar4
use_rainobs=true,
thin_rainobs=true,
thin_mesh_conv=20.,
/

Run 4D-VAR with Accumulated Rainfall Observations

mpirun -np 4 /data1/${USER}/DA/WRFDA/var/build/da_wrfvar.exe_4dvar >&! rainfall.log