The pseudo single ob test is usually the first step to try out WRFDA after you have generated your own be.dat.

Source code

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

WRFDA/var/build/da_wrfvar.exe_3dvar is the executable that will be used in this session.

Choose your working directory

For this exercise you should create /data1/${USER}/DA/singleob and use this as your working directory for this session.

mkdir /data1/${USER}/DA/singleob
cd /data1/${USER}/DA/singleob

Input files

The procedure is the same as running WRFDA-3DVAR with real data (except that the observation file ob.ascii is not required):

ln -fs /data1/${USER}/DA/WRFDA/run/LANDUSE.TBL ./LANDUSE.TBL
ln -fs /wrfhelp/DATA/WRFDA/CONUS60/be/be.dat ./be.dat
ln -fs /wrfhelp/DATA/WRFDA/CONUS60/rc/2008020512/wrfinput_d01 ./fg

Edit namelist.input

Change and add the following namelist.input settings to activate the pseudo single ob test. You can do so by modifying the namelist.input used in the previous WRFDA-3DVAR tutorial case:

cp ../3dvar/namelist.input namelist.input

vi namelist.input

&wrfvar15
num_pseudo = 1,
pseudo_x = 23.0,
pseudo_y = 23.0,
pseudo_z = 14.0,
pseudo_err = 1.0,
pseudo_val = 1.0
/
&wrfvar19
pseudo_var = 'u'
/

Note: pseudo_var can be u, v, t, p, q. If pseudo_var is q, then the reasonable values of pseudo_err and pseudo_val are 0.001 in order to be able to view the analysis increments.

By setting num_pseudo = 1, WRFDA will ignore real data and simply assimilate the pseudo-observation

Run WRFDA (da_wrfvar.exe)

mpirun -np 4 /data1/${USER}/DA/WRFDA/var/build/da_wrfvar.exe_3dvar

Check output

Check the statistics file to view diagnostics related to your pseudo-obs run.

Use ncdiff and ncview to generate and view the analysis increment file.

ncdiff -v U,V,T,QVAPOR,MU,P,PSFC wrfvar_output fg increment.nc
ncview increment.nc

Graphics

Other useful NCL scripts for this exercise:

WRFDA/var/graphics/ncl/WRF-Var_plot.ncl
WRFDA/var/graphics/ncl/WRF_contributed.ncl.test
WRFDA/var/graphics/ncl/psot_xy_auto.ncl
WRFDA/var/graphics/ncl/psot_xz_auto.ncl
WRFDA/var/graphics/ncl/psot_yz_auto.ncl

Other practice

• Response of BE length scaling parameters

  Run single ob test with the following additional parameters

  vi namelist.input (reduce length scale by 50%)

  &wrfvar7
  len_scaling1 = 0.5
  len_scaling2 = 0.5
  len_scaling3 = 0.5
  len_scaling4 = 0.5
  len_scaling5 = 0.5
  /

• Response of changing BE variances

  Run single ob test with the following additional parameters

  vi namelist.input (reduce variance by 75%)

  &wrfvar7
  var_scaling1 = 0.25
  var_scaling2 = 0.25
  var_scaling3 = 0.25
  var_scaling4 = 0.25
  var_scaling5 = 0.25
  /

  If this was successful, you can continue to the next practice case.