[MITgcm-support] noise in high resolution run

[Baylor Fox-Kemper]

Hi Martin,
   I've seen similar noise in W in some runs, but not so obviously in  
U and V.  Have you tried jamartwetpoints?
   Also, are you using no-slip?  We found a few bugs in the sidedrag  
code a while back.  It might be worth revisiting...I suppose it is  
possible that there is a problem elsewhere in the viscosity/viscous  
terms code, but I don't know why it would be localized in space.
   -Baylor


On Mar 30, 2006, at 8:30 AM, Martin Losch wrote:

> Hi,
>
> I seem to have a problem with a 1/6 by 1/6*cos(phi) run with open  
> boundaries. The domain is the Drake Passage. A plot of bathymetry  
> and velocities can be found in
> http://mitgcm.org/~mlosch/noise.png
>
> Whatever friction parameters I have tried (viscAh=1e0 to 2e1 and  
> viscA4=1e8 to 4e10, and similar for diffusivities, I also tried the  
> Leith/Smagorinski variants), I seem to get noise in the north  
> western part of the domain. What worries me is, that
> 1. The noise seems to propagate (compare day 149 to day 214 in the  
> bottom panels of the figure)
> 2. The noise seems to be mainly in the x-direction
>
> I use mom_fluxform. For mom_vecinv the problem is there, too.
> I use USE_ISOTROPIC_SCALING (for viscosities because my y-grid  
> varies with y) and do not use COSINEMETH_III (although that  
> probably doesn't make much of a difference). When I turn off  
> USE_ISOTROPIC_SCALING, the noise is still there, but the x- 
> alignment is slightly less obvious (although very much present). If  
> the noise were deltaX in both directions, I would be concerned  
> about my friction parameters. Here I suspect a problem in the  
> viscosity implementation, but I cannot see how and were.
> There is some noise that is produced by the open boundaries, but  
> that usually goes away. I think that the generation of the noise is  
> connected to the topography around the tip of South America
>
> I wonder if anyone has seen something like this before. What do you  
> think?
>
> Martin
>
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