[MITgcm-support] tutorial_baroclinic_gyre instability

[Martin Losch]

Craig,

in the documentation I find this
http://mitgcm.org/public/r2_manual/latest/online_documents/node120.html
where the stability criteria are discussed. The first is viscAh=4e2, to give a Munk layer of about 100km. You model resolution is 1deg, which is 111km to 55km for your domain (as far as I can see), so contrary to what it says in the documentation, I would argue that the Munk layer is barely resolved, which can lead to "standing" patterns as observed in your your run. 
Try a larger viscAh (but not too large to violate the second CFL like criterion on Ah).

You can also try to use the scaled parameter viscAhGrid. Is there documentation about this? I never can find anything about this parameter so I refer to the header of pkg/mom_common/mom_calc_visc.F

Martin

On Oct 17, 2011, at 1:58 PM, Rye C. wrote:

> Hi,
> 
> My name is Craig D. Rye I'm a PhD student at the National Oceanography Centre, Southampton, UK. I'm a new user of MITgcm.
> 
> I've been playing around with the baroclinic gyre example (which is rather close to the kind of model run I would like to be running). I've taken standard settings and run the model for about 24 years (for spin up). I keep on finding what looks to me like instability in the U and V fields (see attachments). I've tried decreasing the time step but with no change in the results. The model was built in 'build' in the tutorial_baroclinic_gyre folder of verification.
> 
> I was hoping that you might have some suggestions, or atleast I should highlight the problem.
> 
> Attached to this email are the data and SIZE.h files used to initialise the run as well as Jpegs of the eta, U and V fields after 24 years.
> 
> best regards
> 
> Craig
> <eta.jpg><U.jpg><V.jpg><SIZE.h><data>_______________________________________________
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