[MITgcm-devel] problem with 59c

[Martin Losch]

I propose the following: introduce a runtime parameter "zetaMin" that  
defaults to zero (because I think it's a good idea to have zero  
limiting/regularizing by default) that you set to 4e8 in your runs.  
zmin>0 is not needed by the EVP solver (according to Elizabeth)

If you want to experiment with zmin = 0, why don't you try  
seaiceadvscheme = 33 with diff1 = 0, but I don't see why this should  
affect the stability, also you try to increase the accuracy of the  
solver (although you probably don't want that because of cpu time,  
right?)

in general, setting zmin = 0 should have an effect on the velocities  
and only after that on HEFF. (btw, can't find your pdf).

Jinlun, you once recommened setting zmin = 0 (and I agree with your  
recommendation). What's your opinion on this problem?

Martin

On 2 Jul 2007, at 23:53, Dimitris Menemenlis wrote:

> Martin, more on the 59c problem:
>
> The "SEAICEuseDynamics=.false." problem is not "directly" related  
> to the 59c crash.  That is, "SEAICEuseDynamics=.false." crashes in  
> Arctic Ocean even with pre-59c code.
>
> What causes trouble in 59c is the change from ZMIN=4e8 to ZMIN=0.
>
> Figure http://ecco2.jpl.nasa.gov/data1/cube/cube66/crash.pdf
> shows sea ice thickness around Antarctica right before crash.  If  
> you blow up the pdf file, you will see that there are several  
> regions with grid-scale noise in HEFF.  Also shown are time series  
> of HEFF at and near region of maximum thickness showing that  
> thickness reaches 2500 m before model crashes.
>
> So what to do?  Go back to ZMIN=4e8?  Change sea ice advection  
> scheme or diffusivity?  (I am using default advection scheme and  
> diffusivity.) Artificially impose a limit on HEFF?  Something else?
>
> D.
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