[MITgcm-support] OBCS forcing

[Gianmaria Sannino]

Hi Martin,

I'm a little bit confusing because exp4 seems to be 
balanced in terms of volume flux through the four 
boundaries. This is also clear from the OBC files:
  OBNuFile = 'OBmeridU.bin',
  OBSuFile = 'OBmeridU.bin',
  OBWuFile = 'OBzonalU.bin',
  OBEuFile = 'OBzonalU.bin',
  OBWsFile = 'OBzonalS.bin',

The U components both at east and west are the same, while 
the V component at north and south are zero (for default).
Actually my problem is different. I need to simulate a 
channel that is always unbalanced in term of volume flux. 
I guess this is possible to simulate only if you impose 
also the surface elevation at the two boundaries. This is 
what I did, but what happens in the model domain is that 
the free surface does not 'feel' the imposed eta OBC.
Is this behaviour related to the fact that the model is 
using the implicit free surface?

gianmaria

On Tue, 31 Jan 2006 09:05:43 +0100
  Martin Losch <mlosch at awi-bremerhaven.de> wrote:
>Hi Gianmaria,
>
>this should be possible. Have a look at 
>verification/exp4, where there are 4 open boundaries and 
>a net flux.
>I am only guessing, but you may have a problem with an 
>initial shock. Either ramp up your net flux or start from 
>a circulation that is a little more consistent with your 
>boundary conditions,eg. uVel = const = uVel(on open 
>boundary).
>
>Martin
>On Jan 30, 2006, at 6:32 PM, Gianmaria Sannino wrote:
>
>> Hello
>>  
>> I have a query about OBCS.
>>  
>> I'm simulating an east-west channel with a strait in the 
>>middle.
>> This channel is forced through the specification of U,V 
>>and eta at the 
>> two edges in order to simulate a two-layer system with a 
>>net eastward 
>> volume flux. The problem is that  cg2d: Sum(rhs) does 
>>not converge and 
>> the model crash after some time step.
>> This problem does not exist if the net flux is zero.
>> Is the model able to simulate this kind of experiment?
>>  
>>  
>> thanks
>> gianmaria
>>  
>>  
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>
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******************************************************
Gianmaria Sannino   
ENEA (Italian Agency for Energy and Environment)
Climate Project - Ocean Modelling Unit 
SP 91 - via Anguillarese 301
S.M. di Galeria, 00060 ROMA, ITALY
Voice: (+39) 06 3048 6799   Fax: (+39) 06 3048 4264
e-mail: gianmaria.sannino at casaccia.enea.it
URL: http://clima.casaccia.enea.it/staff/sannino/
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