How to use the basic 1DVAR retrieval algorithm with RTTOV-GUI


There is a basic 1DVAR retrieval algorithm available with RTTOV-GUI. It uses the R-matrix and B-matrix of the NWPSAF-1DVAR retrieval software ( see https://nwpsaf.eu/deliverables/1dvar/index.html). In order to be independent from this software, samples of these matrices are available in the RTTOV-GUI directory.


The basic 1DVAR algorithm can only be used for the following instruments :


"airs","iasi","amsua","amsub","mhs","hirs","atms","ssmis","cris"


The observation error R-matrix for iasi metop 2 and iasi metop 1 are identical.

Only one R-matrix for SSMIS is provided.




Running the RTTOV-GUI 1DVAR


RTTOV-GUI 1DVAR works with 2 profiles : a Background profile “Xb” and a True profile “Xt”

The Background Profile is opened in the main RTTOV-GUI window and can be modified as usual.


The True Profile is opened in the specific 1DVAR window and cannot be modified.


If you change the coefficient file with RTTOV-GUI the 1DVAR window is reinitialized.


When you run the RTTOV-GUI your profile must have only 54 levels ( the background error matrix are only available for 54 levels).


The configure 1dvar command of the r1dvar menu becomes available only if you have opened a 54 levels profile and loaded a coefficient file from the previous list of instrument.


It is also possible to run the RTTOV-GUI 1DVAR basic algorithm without running the whole RTTOV-GUI :

example :

python rcontroller/r1dvarController.py -P=${RTTOV_GUI_PROFILE_DIR}/standard54lev_allgas.H5

-s=${RTTOV_GUI_COEFF_DIR}/rttov7pred54L/rtcoef_noaa_19_amsua.dat


The 1DVAR window is initialized in this case with the first profile of

${RTTOV_GUI_PROFILE_DIR}/standard54lev_allgas.H5.



Algorithm Description


Restrictions :


Inputs / selections


When you configure the 1DVAR the R-matrix and B-matrix are read in the ${RTTOV_GUI_PREFIX}/r1DVAR/data directory

It is possible to configure the environment variable NWPSAF_1DVAR_HOME if you want to use another directory (but do not change the sub-directories names and file formats).


  1. Open a true profile Xt selected from the database

  2. Change the value of the scaling factor (fb) for the background errors if necessary

  3. Change the value of the scaling factor (fr) for the observation errors if necessary

  4. Change the value of the maximum random noise if necessary

  5. Click on the RUN 1DVAR button



Computations made by RTTOV-GUI :

  1. Compute brightness temperatures Y(Xt) from Xt (made only at the first step)

  2. Compute and add random noise vector N to Y(Xt) (made only at the first step)

  3. Compute brightness temperatures Y(Xb) from Xb

  4. Compute jacobian matrix K(Xb) and transpose KT(Xb)

  5. Apply scaling factor to background errors B --> fb x B (applied each step to the original B-matrix)

  6. Apply scaling factor to observation errors R --> fr x R (applied each step to the original R-matrix)

  7. Compute linear 1DVAR weights W where W = B . KT . [ K .B . KT + R ](-1)

  8. Compute linear 1DVAR retrieved profile (Xr) Xr = Xb + W . [ ( Y(Xt) + N ) - Y(Xb) ]



The results are displayed in 2 windows :



It is possible to make a maximum of 9 Runs of retrieval.


By clicking the reset button : the 1DVAR window is reinitialized : the background profile is reinitialized (if you a have made some changes on it with the surface window and/or the profile window).