[MITgcm-support] Equatorial Channel from -70 degree to +70 degree

[Yuan Lian]

Hi, Dimitris and Martin,

I just figured out that the problem is actually caused by zonal filter. 
I thought I shoud apply zonal filter if the latitude is greater than 45 
degree. Once the zonal filter was turned off, the code just ran 
smoothly. I feel a little uncomfortable that I have to turn off zonal 
filter. This might cause problems when the channel is close to polar 
region, say, a channel from -80 degree to +80 degree. However I think I 
can just reduce time step if the zonal filter is turned off.

Yuan

Martin Losch wrote:

> Yuan,
>
> the results from
> nPx=8, sNx=32, sNy=93 should be exactly the same (except for round- 
> off error) as those from
> nPx=4, sNx=64, sNy=93,
> nPx=2, sNx=128, sNy=93, and
> nPx=1, sNx=256, sNy=93, regardless of time step.
> When you have NaN's in one case and no NaN's in another, then  
> something else is wrong. What about your nSx/nSy? both should be 1 in  
> all of these examples so that  sNx*nSx*nPx = 256, and sNy*nSy*nPy =  
> 93 for all cases.
>
> Martin
>
> On 4 Oct 2006, at 08:29, Yuan Lian wrote:
>
>> Hi, Dimitris,
>>
>> Thanks. I tried the configuration nPx=8, sNx=32, sNy=93 but the  
>> simulation gave NAN values. I had to reduce the number of grids in  
>> latitude. The configuration nPx=4, sNx=64, sNy=63 worked just fine.  
>> I will try nPx=4, sNx=64, sNy=93 and see how it works. I might try  
>> to use very short time step as well.
>>
>> cheers,
>> Yuan
>>
>> Dimitris Menemenlis wrote:
>>
>>> Hi Yuan,
>>>
>>>> I noticed that, in order to run the simulation, the number of  grid 
>>>> points in
>>>> X direction has to be greater than the number of grids in Y  
>>>> direction in a
>>>> single tile.
>>>
>>>
>>>
>>> There is no such restriction as far as possible model  
>>> configurations are concerned.
>>>
>>>> The number of grids is 256x93
>>>> So the question is: how to configure the "SIZE.h" to run the  
>>>> simulation with
>>>> 4 or 8 processors?
>>>
>>>
>>>
>>> Since 93 is not divisible by 2, and assuming you are using MPI,   
>>> you can have
>>>  nPx=4, sNx=64, sNy=93 and
>>>  nPx=8, sNx=32, sNy=93.
>>>
>>> Cheers, Dimitris
>>>
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>>> MITgcm-support at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>>
>>
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