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Setting up a zoomed simulation is basically telling the model to use a different grid. The standard grid is now 144x142x39 (longitude x latitude x atmospheric levels). If you have developed a zoomed grid which has the same dimensions as that, you can follow the instructions on a different page to install and compile the model. After having done that, you can skip to the Nudge section on this page. If someone else has given you a grid of a different size, you should start from the top here. I am going to assume that you are interested in using a grid which is half a degree resolution over Europe, which is 128x118x39.

Set up for Zoom over Europe in coupled mode LMDZOR

  • Install LMDZOR_v5.2 (using the trunk or one of the branches, as described elsewhere) or LMDZOR_v5 (tag 1.9.5 or 1.9.6)
  • Compile in modipsl/config/LMDZOR_v5.2 using gmake LMD128118-L39


Activate nudging by setting ok_guide=y and add nudging files in BoundaryFiles section List in lmdz.card.
"-" means to remove the line, "+" means to add the line.

 # Nugding : ok_guide=y/n
 # If ok_guide=y, add nudging files(,,,...) in the BoundaryFiles section below.

ERAI nudging files for wind (u and v) have been interpolated to the zoomed grid using the method described here : If you are not using a zoomed grid that has been used previously, you will have to do this yourself. The years 1980 to 2011 have been done for 128x118. They are stored at TGCC here :


This requires a change to COMP/lmdz.card so that libIGCM knows to copy the files before the run. "-" means to remove the line, "+" means to add the line.

+List= (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/NUDGE_FILES/ERAI/${year}/u_${year}${month},,\
+      (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/NUDGE_FILES/ERAI/${year}/v_${year}${month},

The following parameters for nudging result in a strong nudging outside the zoom and a small nudging inside the zoom. Change the PARAM/guide.def to the following :

# ok_guide=y : guidage active
ok_guide=_AUTO_ : DEFFAULT = n
guide_u= y
guide_v= y
guide_T= n
guide_P= n
guide_Q= n

This means that outside the zoom the wind is nudged every 86400*0.05 seconds (about 1h12min), which is considered fairly strong but necessary for an intense zoom. Inside the zoom, the winds are nudged every 10 days.


The aerosols have to be interpolated to the zoomed model grid. The years 1980-2000 for HISTORIQUE run version _v5 have been done. They are found at the standard place : /ccc/work/cont003/dsm/p86ipsl/IGCM/BC/ATM/LMDZ/LMD128118/AR5/HISTORIQUE . You need to change _v3 into _v5 in lmdz.card to use these files.
"-" means to remove the line, "+" means to add the line.

 #      (/dmnfs/cont003/p86ghatt/IGCM_OUT/LMDZOR/NUDGING-CORDEX-AFR/${year}${month}/,,\
 #      (/dmnfs/cont003/p86ghatt/IGCM_OUT/LMDZOR/NUDGING-CORDEX-AFR/${year}${month}/,
 	    (${R_BC}/ATM/${config_UserChoices_TagName}/IPCC_AR5/HISTORIQUE/N2O_1765_2005.txt, N2O.txt),\
 	    (${R_BC}/ATM/${config_UserChoices_TagName}/IPCC_AR5/HISTORIQUE/CFC11_1765_2005.txt, CFC11.txt),\
 	    (${R_BC}/ATM/${config_UserChoices_TagName}/IPCC_AR5/HISTORIQUE/CFC12_1765_2005.txt, CFC12.txt),\
-	    (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/AR5/HISTORIQUE/,
+	    (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/AR5/HISTORIQUE/,
 # With AR5 ozone(tropo + strato from LMDZOR-INCA-REPROBUS simulations)
 List=   (${ARCHIVE}/IGCM_OUT/LMDZ/${CREATE}/ATM/Output/Boundary/${CREATE}_${year},,           1:12:),\
-        (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/AR5/HISTORIQUE/aerosols_11YearsClim_${year}, aerosols${year}.nc, 1:12:), \
+        (${R_BC}/ATM/${config_UserChoices_TagName}/${RESOL_ATM}/AR5/HISTORIQUE/aerosols_11YearsClim_${year}, aerosols${year}.nc, 1:12:), \
         (${ARCHIVE}/IGCM_OUT/LMDZ/${CREATE}/ATM/Output/Boundary/${CREATE}_${year},,     1:12:)

It is also possible to deactivate aerosol forcing. To do so, remove the lines containing aerosols_ from the List section and change lmdz.card to the following :

# manage radiative aerosol effect and ozone 

NB : read_climoz=0 will also deactivate the reading of ozone. Ozone is regridded by the job LMDZ/CREATE_ so this is not necessary to deactivate.

How to run

This should be identical to doing any other coupled run. If it's not, contact someone who is doing coupled runs with a zoomed grid and tell them this page is incomplete and/or wrong.

Further reading

See the page for more information about grids. also has some more information about nudging.

Last modified 3 years ago Last modified on 2020-02-24T16:46:25+01:00