CFL errors caused by the ocean model in real summer cases

[Erenw]

Hi,

I recently attempted to simulate a real case in July for the coastal region in eastern China, but I've encountered issues with CFL errors. Despite trying various methods like reducing the time-step, increasing the epssm, and other techniques I've researched online, I've had no success in resolving these errors. Here are a few key points I've observed:

1. The CFL errors started occurring within the first hour of the simulation.
2. The case is initially driven by ERA5 data, but when I switched to FNL, the errors persisted but the simulation could run for a longer duration.
3. When I disabled the ocean model (by setting the ocean scheme to 0 in my namelist), the case ran successfully.
4. I'm able to run the ocean scheme 1 successfully during January.

I would greatly appreciate your assistance in resolving this issue. Thank you for taking the time to help me, and I wish you a wonderful day!

 

[kwerner]

Hi,

1) In your namelist, I see that you have "smooth_cg_topo" in there, but you have it set to a mis-spelled "true." When you used this option, was 'true' spelled correctly? If not, can you try again with that corrected, and make sure to re-run real.exe before running wrf.exe when using that option.
2) I see that, although you have epssm commented out, it looks like you had it set to 0.2 when you used it. Did you try increasing up to 0.5 to see if that made any difference?
3) You mentioned that you decreased the time_step. How much did you try decreasing it?
4) Can you let me know which version of WRF you are running?
5) Will you also send your rsl files so I can take a look? You can package them all together into a single *.tar file and just attach that.
6) Can you also send your namelist.wps file so I can take a look at the domain set-up?

Thanks!

 

[Erenw]

Thank you for your prompt response. The issue was resolved by modifying the surface physics parameter to "sf_surface_physics = 3" instead of using the Noah-mp scheme (2 or 4). It seems that the Noah land surface scheme may not be fully compatible with the ocean model. While I did not delve deeper into the specific reasons behind this incompatibility, I hope someone with more expertise can provide a more detailed explanation in the future.