[MITgcm-support] obcs for ptracers

[Nataliya Stashchuk]

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
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support

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