[MITgcm-support] ice layer modeling -> cube corners?

[Elja Huibregtse]

Hi Dimitris, Martin,

Thank you very much for your help:

>> In your output file, do:
>> grep advcfl_ STDOUT.0000
The values are all well below zero (1E-3), only for the last 2 timesteps they increase rapidly and become larger that 1. DeltaT is in my case 100 seconds.

>> One thing that you can do to test above hypothesis is to turn off  
>> sea ice dynamics and see if it helps.
>> SEAICEuseDYNAMICS  = .FALSE.,
I turned this parameter off, and the odd 'corner-behavior' indeed dissapeared. (Unfortunately, the model still became instable.) But I am wondering what is going on, now. Does this mean that the seaice thickness only depends on thermodynamics and that the seaice does not respond to the prescribed tidal potential?  

>>it's correct, that we never cared about cube corners in the sea-ice  
>>model, but in my tests, (with the llc-configuration), I did not have  
>>any problems so far, especially not at coarse resolution.
Martin, I am using the 'global_ocean.cs32x15' configuration. What is the difference between your llc-configuration and the global_ocean.cs32x15?  

My goal is to study the ocean dynamics, influenced by a strong tidal potential. I expect that the seaice plays an important role (because the forcing works on the ice, as well). So, I would like to take the seaice dynamics into account. What would you recommend: using another model, like the llc-configuration or ..?

Thanks in advance!

Elja


-----Oorspronkelijk bericht-----
Van: mitgcm-support-bounces at mitgcm.org namens Martin Losch
Verzonden: ma 7/21/2008 9:45
Aan: mitgcm-support at mitgcm.org
Onderwerp: Re: [MITgcm-support] ice layer modeling -> cube corners?
 
Hi Elja, Dimitris,

it's correct, that we never cared about cube corners in the sea-ice  
model, but in my tests, (with the llc-configuration), I did not have  
any problems so far, especially not at coarse resolution.

Martin

On 18 Jul 2008, at 15:42, Dimitris Menemenlis wrote:

> Elja, the correct overlap in your case is OLx=Oly=8, I think.   You  
> can test this by gradually increasing the overlap for a very short  
> problem without optimization, until the pickup files are bit- 
> identical.  But I don't think that this is what causes trouble at  
> the corners.  The change in the solution from OLx 5 to 8 will be  
> very small.
>
> The corners of the cube have smaller dimensions than the rest of  
> the cube so it's easier to violate CFL conditions.  What are your  
> typical velocities, UVEL, VVEL, WVEL, relative to your grid  
> dimensions, dx, dy, dz?
>
> In your output file, do:
> grep advcfl_ STDOUT.0000
>
> If any of these values gets much larger than 1, then you may have  
> to decrease your deltaT even further.
>
> But deltaT is already quite small in your case if I remember  
> correctly so this may not be the problem.
>
> A second possibility is that sea ice model will not work at the  
> corners.  All the tests that I have run with sea ice model, the ice  
> never gets close to the corners.  In particular, the metric terms  
> are ignored in the sea ice dynamics, so close to the corners I have  
> no idea what will happen.  Also, I don't think that the ice  
> momentum equations are compatible with corners.
>
> Does anyone else on this list have experience with running the sea  
> ice model across the cube corners?
>
> One thing that you can do to test above hypothesis is to turn off  
> sea ice dynamics and see if it helps.
>
> SEAICEuseDYNAMICS  = .FALSE.,
>
> in data.seaice
>
> Dimitris Menemenlis
> DMenemenlis at gmail.com
>
> On Jul 18, 2008, at 6:00 AM, Elja Huibregtse wrote:
>
>> Unfortunately, I still didn't find the solution to fix my unstable  
>> ocean+ice model. While checking the data, I found, however, that  
>> velocity-fields show deviant behavior at the corners of the cube  
>> (I use a cubed sphere configuration). I attached one horizontal  
>> velocity plot, where this behavior is clearly visible. The model  
>> becomes, as expected, unstable in one of these 'corner-regions'  
>> and blows up.
>>
>> Could there be something wrong with the coupling between the  
>> tiles? Or do I need a larger overlap (in my case: OLx=Oly=5)?
>> Do you have any idea what is wrong and how to fix it?
>
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