[MITgcm-support] viscosities

[Baylor Fox-Kemper]

Hi Lina,
   Martin is correct that using the viscAhGrid=1 or viscA4grid=1 may  
do what you want.  If that doesn't work, though, you probably want to  
use Smagorinsky.  Just set viscC2Smag=1 and then tune around that.   
You can also use those together.  I'd recommend something like

viscA4Grid=0.01
viscC2Smag=1.

This will get rid of noise with a background biharmonic viscosity and  
then use an harmonic Smagorinsky viscosity for the bulk of the  
viscous effects.
  Cheers,
    -Baylor

On Jan 10, 2007, at 10:57 AM, lina sitz wrote:

> Hi,
> I'm Lina Sitz and I'm new using MITgcm. I'm studying the vortex- 
> pair formation in a basin, product of a tidal-jet arriving from a  
> channel.
> Maximum velocities of the jet are 1 m/seg approximately and the  
> tidal period is 12 hs. The eddies have a radio of 2.5 km  
> approximately. The horizontal dimension of the region is 15x30 km  
> and the depth is 25 m.
> Because of the size of the channel and the dimension of the problem  
> I would like to use a variable resolution (between 50 and 400 m),  
> but I would like to know what kind of viscosity I must to set, when  
> running MITgcm. I tried with different values of constant  
> viscosities, taking into acount the stabilities constraint, but the  
> solution have noise, even using a grid with constant resolution (50  
> m). I don't know if in this kind of problem is more adequate to use  
> Smagorinsky or Leith viscosities or if the values that I'm using  
> are not correct.
>
> I apologize because of my English and I would appreciate any  
> suggestion.
>
> Thanks in advance!
>
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