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(RESOLVED) Allowed range for epssm

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I am running WRF version 4.1.3. over a mountain region. Due to CFL issues, I am trying to reduce the time step and modify the epssm parameter (terrain smoothing is not an option for me as I need the exact elevation), and I set w_damping = 1 and damp_opt = 3 (needed for my usecase). I have 5 domains (25 km, 5 km, 1 km, 200 m, 40 m), and the WRF run only works if I set epssm = 0.1, 0.1, 0.9, 1.7, 2.1.

I have read that increasing epssm from default 0.1 to 0.5 or even 1.0 can help and that epssm is a sound-wave damper that can stabilize slope treatment by dynamics and has little other effect.

Can you please let me know if epssm values as high as 2.1 are also reasonable in that case and if those high values really don't have much other effect on weather variables? In other words, will my results with a WRF run with epssm values of 2.1 still be meaningful?

I appreciate your help! Thanks a lot for your time.
Our physics/dynamics expert has always instructed that epssm should not be set higher than 0.5. epssm is used to slightly forward the centering of the vertical pressure gradient (or sound waves) in an effort to damp 3-d divergence. Altering it anymore than ‘slightly’ can begin to provide inaccuracy.