[MITgcm-devel] problem with 59c

[Jinlun Zhang]

I am not sure what sea ice model is used here. If it is EVP, I don't 
really know. But if it is LSR, zmin has to be set to zero all the time. 
And if things blow up, zmin=0 is unlikely the problem. Something else.
Jinlun

Martin Losch wrote:

> 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.
>