The pseudo single ob test is usually the first step to try out WRFDA after you have generated your own be.dat. It is a very useful tool, which can be used to investigate your choice of background error and its impact on your analysis. See the Background Error presentation for more information (starting on slide 22).

Source code

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

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

Choose your working directory

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

mkdir /kumquat/users/${USER}/DA/singleob
cd /kumquat/users/${USER}/DA/singleob

Input files

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

ln -fs /kumquat/users/${USER}/DA/WRFDA/run/LANDUSE.TBL ./LANDUSE.TBL
ln -fs /kumquat/users/${USER}/DA/gen_be/workdir/be.dat ./be.dat
ln -fs /kumquat/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 reasonable values of pseudo_err and pseudo_val are 0.001 rather than 1.0.

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

Run WRFDA (da_wrfvar.exe)

mpirun -np 6 /kumquat/users/${USER}/DA/WRFDA/var/build/da_wrfvar.exe

Check output

As with every run of WRFDA, you should first make sure that the rsl.out.0000 file ends with "*** WRF-Var completed successfully ***".

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 To the right you can see what your pressure perturbation should look like with the above settings (click the image for a larger version). Try using "v" instead of "u" as your test variable. How would you expect the pressure perturbation to change? (click here to see)

Graphics

Use ncdiff and ncview to generate and view the analysis increment file. Some useful NCL scripts for this exercise are: /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/WRF-Var_plot.ncl /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/WRF_contributed.ncl.test /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/psot_xy_auto.ncl /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/psot_xz_auto.ncl /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/psot_yz_auto.ncl /kumquat/wrfhelp/DATA/WRFDA/TOOLS/graphics/ncl/psot_h.ncl The plot at right was generated using psot_h.ncl using the following settings: works = "pdf" expt = "" directory = "/kumquat/users/$USER/DA/singleob/" first_guess = addfile(directory+"fg.nc", "r") analysis = addfile(directory+"wrfvar_output.nc", "r") kl=12 Using these settings as a guide, try out the other scripts listed above.

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 have reached the end of the basic day 1 exercises! If you have extra time remaining, there are some more exercises you can try:

Try the additional exercises from the day 1 practice session; they can be found at the bottom of each page



Try compiling WRFDA yourself

After you have run the hybrid tutorial case, try running PSOT with hybrid assimilation. This exercise can be found at that page.