damping filters?

[pattim]

I'm getting some CFL violations at high levels in the domain. Which filter is recommended to minimize these effects?

Thank You!

[meteoadriatic]

Try

damp_opt = 3
w_damping = 1
dampcoef = 0.2

If that doesn't help your time step is probably too large.

[pattim]

Thanks very much meteo! I hope you are well. I have also found that increasing the number of acoustic substeps helps in many instances (increasing TIME_STEP_SOUND = 4 to 8 or 16) - but making it too big slows down the calculations. So I wanted to try the filtering you and some others on this forum had mentioned.

There are filters for high latitudes, but I thought you guyz mentioned a top-of-atmosphere filter - I think my CFL violations occur at top levels. Do you see that often in fine-gridded nested domains? (1km or less)

Have a great weekend!
Patti

[meteoadriatic]

Yes I did have problems few levels under the top, and fixed that with values I given above.

Maybe I can be of better help if you copy/paste exact cfl violation messages from the log.

[pattim]

Yes I did have problems few levels under the top, and fixed that with values I given above.

Maybe I can be of better help if you copy/paste exact cfl violation messages from the log.

Thank you for the replies on damping. I am having high level CFL violations show up before a run crashes. I am trying your suggestions right now!

Thanks - Patricia

EDIT: That didn't help - trying to adjust to DAMPCOEF = 0.1