damping filters?

Forum dedicated to older versions of EMS package (WRFEMS v3.2, v3.1 or older). Support is user-to-user based, so please help others if you can.
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pattim
Posts: 157
Joined: Sun Jun 24, 2012 8:42 pm
Location: Los Angeles, CA, USA

damping filters?

Post by pattim » Tue May 14, 2013 2:55 pm

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

Thank You!

meteoadriatic
Posts: 1512
Joined: Wed Aug 19, 2009 10:05 am

Re: damping filters?

Post by meteoadriatic » Tue May 14, 2013 4:28 pm

Try

damp_opt = 3
w_damping = 1
dampcoef = 0.2

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

pattim
Posts: 157
Joined: Sun Jun 24, 2012 8:42 pm
Location: Los Angeles, CA, USA

Re: damping filters?

Post by pattim » Wed May 15, 2013 3:11 pm

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
Posts: 1512
Joined: Wed Aug 19, 2009 10:05 am

Re: damping filters?

Post by meteoadriatic » Wed May 15, 2013 5:15 pm

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
Posts: 157
Joined: Sun Jun 24, 2012 8:42 pm
Location: Los Angeles, CA, USA

Re: damping filters?

Post by pattim » Sun Jun 02, 2013 7:04 pm

meteoadriatic wrote: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

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