[MITgcm-support] how to control obcs balance flow ?

[李志远]

Thank you for your quick reply,  Matthew !
I know that if open boundary flow in and flow out are not balanced , after a long time,the ssh will keep increasing or decreasing . So , in order to get a good ssh result ,
open boundary flow in and flow out must be balanced . I can compute the total flow into/out  the model through each open boundary grid u ,v . I wonder if I can  adjust the u,v to make total flow into the model is absolutely equal to total flow out the model  at open boundary ? If so ,ssh will not keep increasing or decreasing .


thank you !
YOURS  LI ZHI 
BEST REGARDS !








At 2014-04-19 00:00:01,mitgcm-support-request at mitgcm.org wrote:
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>   1. Re: how to control obcs balance flow ? (Matthew Mazloff)
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>----------------------------------------------------------------------
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>Message: 1
>Date: Thu, 17 Apr 2014 21:18:43 -0700
>From: Matthew Mazloff <mmazloff at ucsd.edu>
>To: <mitgcm-support at mitgcm.org>
>Subject: Re: [MITgcm-support] how to control obcs balance flow ?
>Message-ID: <649BFBA3-CBC6-4105-802F-5A626BE61CE3 at ucsd.edu>
>Content-Type: text/plain; charset="utf-8"
>
>Hello
>
>I correct OBCS as part of preprocessing and don't rely on ALLOW_OBCS_BALANCE.
>
>Basically you know the inflow/outflow that you want -- so correct your prescribed obcs to have that magnitude inflow.
>
>E.g. if you have a solution from another model that you are gonna make your southern boundary, first interpolate that field to your new model grid. Then make the net prescribed flow through a part of that (e.g. over each 1 degree section) to be the exact same as the original. This usually requires a perturbation to the velocity of about .001cm/s. But if you don't make that correction SSH will run away from you?.so its a vital correction.
>
>Matt
>
>
>On Apr 16, 2014, at 7:39 PM, ??? <oceanlizy at 163.com> wrote:
>
>> From: Li zhiyuan <oceanlizy at 163.com>
>> >To: MITgcm <mitgcm-support at mitgcm.org>
>> >Subject:"how to control obcs balance flow ? "
>> Dear MITgcm users:
>>       my model has two open boundarys in south and east . I have "#define ALLOW_OBCS_BALANCE " in the OBCS_OPTIONS.h  , but the rusults revealed that  ssh is very high , even up to 2 m !!  I think it is because  the flow in and out  at open boundarys  are not balanced ,so ssh is anomalous. How to control  balance flow  at open boundarys ? 
>> Thank you for your quick reply !
>> Yours  Li zhiyuan
>> Best regards  ! 
>> 
>> 
>> 
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