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cfl error when running with nudging option

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kaelel18

Member
Hi WRF team. I am running a simulation which uses nudging option and restart option as was recommended for running long simulation. Without the nudging option and restart, wrf is able to complete the simulation without any errors. But when I added the two options, it started to become unstable. I have reduced the time step, added epssm, and smooth topo, but I immediately get cfl errors after 5 minutes of run time. I am not sure if it has something to do with my nudging entry. I am attaching the namelist.input and rsl errors for your reference. As always, thanks!
 

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Hi,
I'm not sure what you mean by 'adding the restart option.' Do you mean setting a restart interval? If so, having the model output restart files should not have anything to do with the CFL errors. Can you try just turning off nudging to see if that is the culprit?
 
Hi kwerner. Apologies, I meant restart interval. I turned off nudging but with restart interval and it is working just fine.

I guess it has something to do with the nudging. Although, I needed to include nudging in the simulation since I will be doing a long simulation time. How can this be resolved?
 
Hi,
I think the problem is your settings for namelist variables guv, gt, and gq in the &fdda section. A good recommended setting is 0.0003, and you have each of these set to 1.0, which is MUCH larger than the recommendation. I ran tests and the runs always stop with CFL errors when they are set to 1, but the runs complete successfully when using 0.0003.
 
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