[MITgcm-support] obcs for ptracers

[Martin Losch]

You can do that in quite the same way as for T and S:
either you hard-code is in obcs_calc (instead OBCt=10. you use  
OBSptr=2. or so),
or you prescribe a file with these open boundary conditions as done  
in exp4 (I prefer this, because you won't have to recompile the code).

Martin
On 24 Apr 2008, at 15:50, Nataliya Stashchuk wrote:

> Martin,
>
> In verification/exp4/input data.ptracers  I found the following:
> ---------------------------------------------------------------------- 
> ----------------------------------------------
>
> # This set-up is supposed to mimic salinity. That is, initially
> # PTRACER(:,:,:,1) is identical to salinity, except that the
> # open boundary conditions are different, so that PTRACER(:,:,:,1)  
> evolves
> # differently than salinity.
>  &PTRACERS_PARM01
>  PTRACERS_numInUse=1,
>  PTRACERS_initialFile='S.init',
>  PTRACERS_names(1)='salt_mimic',
>  &
> ---------------------------------------------------------------------- 
> ------------------------------------------------
> This means that in this experiment salinity is used as a tracer. In  
> such a case it is very simple to fix tracer at open boundary  
> condition.
> For example if I want to fix temperature as 10 and salinity  
> (tracer) as 1 at eastern boundary I can change two last lines in  
> obcs_calc.F like this
>
> ---------------------------------------------------------------------- 
> ------------------------
>
> #ifdef ALLOW_OBCS_EAST
> C     Eastern OB
> #ifdef ALLOW_DEBUG
>       IF (debugMode) CALL DEBUG_MSG('OBCS_CALC: East',myThid)
> #endif
>       IF (useOrlanskiEast) THEN
> #ifdef ALLOW_ORLANSKI
>         CALL ORLANSKI_EAST(
>      &          bi, bj, futureTime,
>      &          uVel, vVel, wVel, theta, salt,
>      &          myThid )
> #endif
>       ELSE
>         DO K=1,Nr
>           DO J=1-Oly,sNy+Oly
>             I_obc=OB_Ie(J,bi,bj)
>             IF (I_obc.ne.0) THEN
>               OBEu(J,K,bi,bj)=0.
>               OBEv(J,K,bi,bj)=0.
>
>               OBEt(J,K,bi,bj)=10.
>               OBEs(J,K,bi,bj)=1.
>
> ---------------------------------------------------------------------- 
> ----------------------------------------------------
>
> In my case I use both T and S to find density. Thus I will use  
> tracer as additional variable and I must fix its value at a boundary.
>
> How I can do this?
>
> Nataliya
>
>
>
>
> -----Original Message-----
> From: mitgcm-support-bounces at mitgcm.org [mailto:mitgcm-support- 
> bounces at mitgcm.org] On Behalf Of Martin Losch
> Sent: 24 April 2008 13:28
> To: mitgcm-support at mitgcm.org
> Subject: Re: [MITgcm-support] obcs for ptracers
>
> Nataliya,
> I am not quite sure what exactly it is that you want to do, but you
> can do two things to prescribe tracer concentration:
> 1. with the rbcs package you can restore to some climatology (or
> fixed in time) fields with a certain time scale
> 2. with the obcs package you can prescribe open boundary values (also
> for passive tracers in ptracers), see verification/exp4 for a simple
> example.
>
> Martin
>
> On 24 Apr 2008, at 13:31, Nataliya Stashchuk wrote:
>
>> Dear MITgcm users,
>>
>>
>>
>> The temperature and salinity  are fixed at one of the open
>> boundaries in my computation area. EOS is used as Knudsen  equation
>> for density in my runs.
>>
>>
>>
>> I will be happy to use the tracer in my investigation and need to
>> fix the value of the tracer at the open boundary during the run. My
>> investigation of ptracer  pkg did not give me a clue how to do
>> this. Could you help?
>>
>>
>>
>>
>>
>> Regards,
>>
>>
>>
>> Nataliya
>>
>> _______________________________________________
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>> MITgcm-support at mitgcm.org
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>
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