[MITgcm-support] Natural Boundary Conditions

[Matthew Mazloff]

Hello,

With closed boundaries and useRealFreshWaterFlux=false cg2d sum 
converges to the target residual. 
cg2dMaxIters=500,
cg2dTargetResidual=1.E-10,

With either useRealFreshWaterFlux=false or open boundaries turned on, 
cg2d does not even come close to reaching this value
e.g.:     cg2d: Sum(rhs),rhsMax =  -3.48350328484614E-01  
2.56260817486123E+00

While trying to figure this out I came across this thread and thought 
someone may be able to give me some advice.

Thanks,
Matt

>
> ----- Original Message ----- From: "Chris Hill" <cnh at mit.edu>
> To: <mitgcm-support at mitgcm.org>
> Sent: Monday, July 11, 2005 9:40 PM
> Subject: Re: [MITgcm-support] Natural Boundary Conditions
>
>
>> G.,
>>
>>  We have one theory as to what might be going on.
>>  Can you send the sum(RHS) time series you get to the list when you 
>> have a moment.
>>
>> Thanks,
>>
>> Chris
>> Gianmaria Sannino wrote:
>>
>>> ciao Martin,
>>>
>>> thanks, but I've alread seen that exp.
>>> What actually happens is that cg2d slowly increases to values that 
>>> are > 0. I'm using also the exact conservation option.
>>> When the freshwaterflux is FALSE the cg2d is 10^-13 !!
>>>
>>> do you have other ideas??
>>>
>>> a presto
>>> gm
>>>
>>>
>>> ----- Original Message ----- From: "Martin Losch" 
>>> <mlosch at awi-bremerhaven.de>
>>> To: <mitgcm-support at mitgcm.org>
>>> Sent: Monday, July 11, 2005 8:52 AM
>>> Subject: Re: [MITgcm-support] Natural Boundary Conditions
>>>
>>>
>>>> HI Gianmaria,
>>>>
>>>> have a look at, e.g., verification/global_ocean.90x40x15/ (an 
>>>> experiment which uses "realFreshWaterFlux=.true.") and compare the 
>>>> data-files and CPP-Flags etc with your set-up. Maybe that can give 
>>>> your a clue, why your run is blowing up (is it really blowing up?)
>>>>
>>>> Martin
>>>>
>>>> On Jul 10, 2005, at 5:38 PM, Gianmaria Sannino wrote:
>>>>
>>>>> Dear all,
>>>>>
>>>>> I'm trying to use the Natural Boundary Conditions in the MITgcm.
>>>>> To do this I've set useRealFreshWaterFlux to TRUE in the data 
>>>>> file, but after that the cg2d variable increases toward unstable 
>>>>> values respect to the simulation with useRealFreshWaterFlux set to 
>>>>> FALSE. I've also used the non linear free surface option.
>>>>> Is there anyone can help me?
>>>>>
>>>>> thanks
>>>>> gianmaria
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>> MITgcm-support at mitgcm.org
>>>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>>>
>>>>
>>>>
>>>>
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>>>
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>>
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