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Request for Guidance on CFL Errors in WRF Simulations

M

met-sree

Member
Dear all,
We are encountering CFL errors while running WRF simulations, likely due to steep topography in the region. Based on earlier suggestions, we have already tried the following:
  • Reduced the time step (by a factor of three). For example, with a 9 km domain resolution, instead of using the usual 9 × 6, we set it to 12. The model runs with this setting, but the simulations take significantly longer.
  • Reduced the number of vertical levels (to 34).
We would greatly appreciate any further guidance on how to overcome this issue.

Thank you,
Sree
 
met-sree said:
Dear all,
We are encountering CFL errors while running WRF simulations, likely due to steep topography in the region. Based on earlier suggestions, we have already tried the following:
  • Reduced the time step (by a factor of three). For example, with a 9 km domain resolution, instead of using the usual 9 × 6, we set it to 12. The model runs with this setting, but the simulations take significantly longer.
  • Reduced the number of vertical levels (to 34).
We would greatly appreciate any further guidance on how to overcome this issue.

Thank you,
Sree
Click to expand...
can you please upload your namelist.input and namelist.wps as well as your rsl.out and rsl.error files in a zip file?
 
Okay here's a few things that might help

1. w_damping = 0 ---> 1 (helps control cfl errors)
2. radt = 10,10 ----> 9,9 (doesn't affect cfl errors)
3. add epssm = 0.5 (due to the Himalayas this helps reduce the cfl errors)
 
Hi Sree,
Over deep terrain areas, we recommend using a larger value of epssm, for example epssm=0.9. Can you try and let me know whether it works for you?
 
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