Up to Starting with OASIS3-MCT (first steps, tutorial, ...)
Hi, I am working at Meteo-France with Cindy Lebeaupin and I plan to couple AROME-WMED to NEMO using OASIS3-MCT. I downloaded the sources of OASIS3-MCT and compiled it on Beaufix. I decided to compile and run the tutorial toy located in /oasis3-mct/examples/ to get more familiar with the coupler. I could not run the toy model. It seems that the models stop at the first time step in their 'get(t=0)'. If I put LAG=dt in the namcouple for both coupling fields it works, but what is the impact of the LAG on the global simulation ? By the way putting LAG=0 in the namcouple do not solve the problem. Thanks, Regards, Rosalie
Hi Rosalie, Compiling and running the tutorial toy before working on the real coupled models is the good approach. You should also use the toy test_interpolation with your grids, to test the quality of the interpolations you will use in your real coupled model. The deadlock you observe is normal as both models begin their exchanges with an oasis_get at t=0. In this case the models must read their data in a restart file at t=0 and the only way to do that is to specify a LAG > 0 in the namcouple (the namcouple has no LAG > 0 in the initial sources). "fdocn.nc" is the restart file for model1 and "fdatm.nc" is the restart file for model2. With LAG=dt for both coupling fields in the namcouple, both models read their data at t=0 in their restart files and write a restart file at the end of the simulation for the next run. This configuration is the one that is usually used in the real coupled models. Defining LAG=dt implies that there will be a shift in time between the oasis_put and the oasis_get. If I call tCPL a coupling time, the oasis_put done at tCPL + LAG will match the oasis_get done at tCPL. You have more informations on the LAG in the User Guide https://oasis.cerfacs.fr/wp-content/uploads/sites/114/2021/02/GLOBC-Valcke_TR_OASIS3-MCT_2.0_2013.pdf, section 2.10 To end with, as you observed, LAG=0 does not do anything and does not solve the problem. Best regards, Laure
Picture with a run with no LAG and a run with LAG : https://oasis.cerfacs.fr/wp-content/uploads/sites/114/2021/07/Runtime-and-LAG.pdf
