[MITgcm-support] Some questions on Smagorinsky and KPP

[Martin Losch]

Abbas,
the Smagorinsky/Leith viscosities are quite well documented, e.g.  
here <http://mitgcm.org/r2_manual/latest/online_documents/ 
node85.html> and in the code (pkg/mom_common/mom_calc_visc.F). I  
recommend reading the documentation.
1.+2.:For non-hydrostatic code, the horizontal viscosities of  
vertical velocities are also properly computed, but the vertical  
viscosities are not part of the scheme (not for any velocity component)
3. yes, you can set diffusivities to zero with temp/saltAdvScheme=33,  
(and 77 and 7). These schemes are stable, but you may want to  
introduce some extra diffusion for physical reasons.
4. this is trial and error. There are a few recommendations in  
mom_calc_visc.F.

Further, there was a long discussion on this list a while ago, which  
I recommend to read, it starts here:
<http://forge.csail.mit.edu/pipermail/mitgcm-support/2006-November/ 
004459.html>
In particular I had a noise problem with smag+kpp, which Baylor  
nicely explained here:
<http://forge.csail.mit.edu/pipermail/mitgcm-support/2006-November/ 
004469.html>
Also when you type
"leith site:http://forge.csail.mit.edu/pipermail/mitgcm-support/"
into google (I think "our" search mask, which is supposed to do  
exactly that still does not work) you'll get a lot of discussion  
about this topic.

Martin

On 7 Jul 2008, at 23:25, Abbas Dorostkar wrote:

> Hi all,
> I would like to use Smagorinsky, KPP and 33 advection schemes in my  
> set
> up. I have a few questions. It would be great if someone could help:
> 1. Are Smagorinsky-scaled vertical viscosities implemented in the  
> model?
> 2. Are the Smagorinsky or Leith schemes implemented in non-hydrostatic
> mode?
> 3. Using Kpp and 33 advection schemes, I think I can eliminate
> horizontal and vertical diffusivities. Is that right?
> 4. What is the best value for viscC2Smag to start? How can I calibrate
> this coefficient?
> Thanks in advance,
> Abbas
>
>
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