[MITgcm-support] MITgcm-support] what is obcs balance?

[Martin Losch]

Hi there,
you are right, but it's difficult to code it in a way that is general (where do you add the imbalance? what do you do if someone has only two open boundaries allowed? etc.). Use this piece of code as a template for your own modifications, if you like.
I usually do the balancing offline, when I create the boundary files for u and v.


Martin


----- Original Message -----
From: David Hebert <david.hebert.ctr at nrlssc.navy.mil>
Date: Tuesday, July 14, 2009 19:51
Subject: Re: [MITgcm-support] MITgcm-support] what is obcs balance?
To: mitgcm-support at mitgcm.org

> It appears the way the code is written the sum of the flux 
> across each face is zero. I don't see anywhere in the code where 
> the sum from all faces is used to make any sort of correction to 
> OBC values.  I agree completely that it is the total flux 
> in/out of a domain that is of interest, not each  face 
> independently.
> David
> 
> Nico Wienders wrote:
> >
> >
> >I still don't understand. LOW_OBCS_BALANCE=.TRUE.
> >means:
> >
> >that the the flow across each face with be equal to zero?
> >
> >or
> >
> >That the sum of the flow across each (4) face will be zero?
> >(which would have more physical justification).
> >
> >
> >
> >
> >
> >
> >On Jul 14, 2009, at 10:17 AM, Martin Losch wrote:
> >
> >>David,
> >>
> >>you interpreted the code correctly, and you also observed 
> correctly that this is not documented in the manual.
> >>
> >>Martin
> >>
> >>On Jul 14, 2009, at 3:36 PM, David Hebert wrote:
> >>
> >>>Hi everyone,
> >>>
> >>>Thanks Jean-Michel for clarifying the #undef NONLIN_FRSURF flag.
> >>>
> >>>I am now looking at obcs_calc.F and the portions related to 
> ALLOW_OBCS_BALANCE. If I am not mistaken, if I use 
> ALLOW_OBCS_BALANCE, the code computes the flux through one 
> particular face as the sum of  area * OB[EWNS][uv].  
> If the sum over the whole face is not zero, the code then 
> subtracts the sum/area off that particular face, forcing the 
> boundary flux to be zero. Is this true? If not, can someone 
> perhaps provide a description of what is happening? I am not 
> seeing this description in the manual.
> >>>
> >>>Thank you,
> >>>
> >>>David 
> 
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support

Martin Losch
Alfred Wegener Institute 
Postfach 120161, 27515 Bremerhaven, Germany; 
Tel./Fax: ++49(0471)4831-1872/1797




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20090714/b2d43191/attachment.htm>