[MITgcm-support] MITgcm-support Digest, Vol 167, Issue 21

Wed May 24 08:57:15 EDT 2017

Hi,
Thank you for your advice. I have some further questions.

@Jean-Michel,
Yes, I am compiling with #define USE_OLD_EXTERNAL_FORCING.  Regarding
apply_forcing.F, can I still provide bulk forcing in a similar fashion
there or are there significant changes? From what I could see the momentum
forcing terms seemed to be the same, but I may be missing something?

@Jody: Can I force the boundary with Orlanski using the OBCStides option?
Further, for  wave generation, shouldn't prescribing the tidal forcing only
at the boundaries not generate waves since there is a phase lag within the
domain and all regions won't experience the same velocity at the same time.

-Hanut

On Wed, May 24, 2017 at 1:03 PM, <mitgcm-support-request at mitgcm.org> wrote:

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> Today's Topics:
>
>    1. Tidal forcing with Orlanski boundary conditions.
>       (Hanut Vemulapalli)
>    2. Re: Tidal forcing with Orlanski boundary  conditions. (Jody Klymak)
>    3. Re: Tidal forcing with Orlanski boundary  conditions.
>       (Jean-Michel Campin)
>    4. Re: ideal age tracer (Alexandre Pohl)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 23 May 2017 22:42:29 +0530
> From: Hanut Vemulapalli <hanut2 at gmail.com>
> To: mitgcm-support at mitgcm.org
> Subject: [MITgcm-support] Tidal forcing with Orlanski boundary
>         conditions.
> Message-ID:
>         <CAC9SbcbjP_WKpSiWP_p=KGw7+HXv5E3qgvuPQyxL0XwhECbtHg@
> mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi all,
>
> I am trying to simulate gravity waves produced by a gaussian topography in
> uniform stratificaiton. I have a 2D simulation with unit depth in the
> y-coordinate. I am giving tidal forcing to the model in
> code/external_forcing.F by adding the following lines .
>
> DO j=0,sNy+1
>   DO i=1,sNx+1
>           gU(i,j,kLev,bi,bj) = gU(i,j,kLev,bi,bj) +
> 0.02*0.00014*cos(0.00014*myTime)
>   ENDDO
> ENDDO
>
>
> I am prescribing Orlanski boundary condition at the east and west
> boundaries.
> However, the velocity magnitude tends to very small values of the order
> 1E-5 times the tidal amplitude (i.e 1E-12) once I prescribe open boundary
> condition at the east and west boundaries.
> Can anyone tell me where I am going wrong.
>
> Thanks in advance.
>
> Best regards
> Hanut
>
>
>
>
>   <https://mailtrack.io/> Sent with Mailtrack
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> ------------------------------
>
> Message: 2
> Date: Tue, 23 May 2017 10:27:21 -0700
> From: Jody Klymak <jklymak at uvic.ca>
> To: mitgcm-support at mitgcm.org
> Subject: Re: [MITgcm-support] Tidal forcing with Orlanski boundary
>         conditions.
> Message-ID: <64DBA29B-9BBC-4315-B5E9-3854BBD74356 at uvic.ca>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Hanut,
>
> The boundary conditions need to be altered to force the flow through them
> as well.  Orlanski will allow a mode-1 wave to pass, but without
> modification will set the barotropic velocity to zero.  The body force
> should still move the water around in the interior, but your boundary
> conditions will be set to zero barotropic flow.  I think ye olde internal
> wave examples modify `calc_obcs.F`, but you don?t need to do this anymore.
>
> For a radiating internal wave problem I recommend using obcs or rbcs and
> force a sponged velocity at the boundaries, and I do not use orlanski etc.
> The sponge needs to be wide and gentle enough to absorb internal waves
> without reflection.
>
> An example setup (with steady forcing, but how to setup oscilatory forcing
> should be clear from `gendata.py`) is at
>
> https://github.com/jklymak/MITgcmExampleSteadyGauss <
> https://github.com/jklymak/MITgcmExampleSteadyGauss>
>
> I think you can use the external forcing of the boundary with Orlanski BC
> instead of a sponge.
>
> I think you can also do all this with a body force as well, but you would
> want to be sure that your body force and BC forcing are in sync.
>
> If your domain is long compared to the surface tidal wave, you may also
> want to lag one end of the domain relative to the other to allow the tidal
> waves to be in sync.
>
> Cheers,   Jody
>
>
>
> in data &PARAM03:
>
> `
>
> # Forcing for boundary condition files
>  periodicExternalForcing=.TRUE.,
> # 1/12th M2 tidal period...
>  externForcingPeriod = 3720.,
> # one tidal period (12 records need to be in OBEuFile, etc)
>  externForcingCycle = 44640.,
> `
>
> and in data.obcs:
>
> `
>
> # Open-boundaries
>  &OBCS_PARM01
>  OB_Iwest=1*1,
>  OB_Ieast=1*-1,
>  OB_Jnorth=80*0,
>  OB_Jsouth=80*0,
>  useOBCSsponge=.TRUE.,
>  useOBCSprescribe=.TRUE.,
>  OBEuFile = 'Ue.bin',
>  OBWuFile = 'Uw.bin',
>  OBEtFile = 'Te.bin',
>  OBWtFile = 'Tw.bin',
>  /
>
> # Orlanski parameters
>  &OBCS_PARM02
> /
>
> # Sponge layer parameters
>  &OBCS_PARM03
>  Urelaxobcsinner=1000.,
>  Urelaxobcsbound=100.,
>  Vrelaxobcsinner=1000.0,
>  Vrelaxobcsbound=100.0,
>  spongeThickness=10,
>  /`
>
>
>
>
>
> > On May 23, 2017, at  10:12 AM, Hanut Vemulapalli <hanut2 at gmail.com>
> wrote:
> >
> > Hi all,
> >
> > I am trying to simulate gravity waves produced by a gaussian topography
> in uniform stratificaiton. I have a 2D simulation with unit depth in the
> y-coordinate. I am giving tidal forcing to the model in
> code/external_forcing.F by adding the following lines .
> >
> > DO j=0,sNy+1
> >   DO i=1,sNx+1
> >           gU(i,j,kLev,bi,bj) = gU(i,j,kLev,bi,bj) +
> 0.02*0.00014*cos(0.00014*myTime)
> >   ENDDO
> > ENDDO
> >
> >
> > I am prescribing Orlanski boundary condition at the east and west
> boundaries.
> > However, the velocity magnitude tends to very small values of the order
> 1E-5 times the tidal amplitude (i.e 1E-12) once I prescribe open boundary
> condition at the east and west boundaries.
> > Can anyone tell me where I am going wrong.
> >
> > Thanks in advance.
> >
> > Best regards
> > Hanut
> >
> >
> >
> >
> >  ?  <https://mailtrack.io/>Sent with Mailtrack <
> https://mailtrack.io/install?source=signature&lang=en&
> referral=hanut2 at gmail.com&idSignature=22>_______________
> ________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
>
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> ------------------------------
>
> Message: 3
> Date: Tue, 23 May 2017 14:36:22 -0400
> From: Jean-Michel Campin <jmc at mit.edu>
> To: mitgcm-support at mitgcm.org
> Subject: Re: [MITgcm-support] Tidal forcing with Orlanski boundary
>         conditions.
> Message-ID: <20170523183622.GA30290 at ocean.mit.edu>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Hanut,
>
> Subroutines in external_forcing.F have been retired since Aug 2014
> and replaced with the ones in apply_forcing.F
> They are just kept in case someone has a customized version and want
> to keep it (and in this case, need to compile with #define
> USE_OLD_EXTERNAL_FORCING
> in CPP_OPTIONS.h). Are you in this case ?
>
> Cheers,
> Jean-Michel
>
> On Tue, May 23, 2017 at 10:42:29PM +0530, Hanut Vemulapalli wrote:
> > Hi all,
> >
> > I am trying to simulate gravity waves produced by a gaussian topography
> in
> > uniform stratificaiton. I have a 2D simulation with unit depth in the
> > y-coordinate. I am giving tidal forcing to the model in
> > code/external_forcing.F by adding the following lines .
> >
> > DO j=0,sNy+1
> >   DO i=1,sNx+1
> >           gU(i,j,kLev,bi,bj) = gU(i,j,kLev,bi,bj) +
> > 0.02*0.00014*cos(0.00014*myTime)
> >   ENDDO
> > ENDDO
> >
> >
> > I am prescribing Orlanski boundary condition at the east and west
> > boundaries.
> > However, the velocity magnitude tends to very small values of the order
> > 1E-5 times the tidal amplitude (i.e 1E-12) once I prescribe open boundary
> > condition at the east and west boundaries.
> > Can anyone tell me where I am going wrong.
> >
> > Thanks in advance.
> >
> > Best regards
> > Hanut
> >
> >
> >
> >
> >   <https://mailtrack.io/> Sent with Mailtrack
> > <https://mailtrack.io/install?source=signature&lang=en&
> referral=hanut2 at gmail.com&idSignature=22>
>
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 24 May 2017 09:39:46 +0200
> From: Alexandre Pohl <pohl at cerege.fr>
> To: mitgcm-support at mitgcm.org
> Subject: Re: [MITgcm-support] ideal age tracer
> Message-ID: <D4AF3406-1AD2-4D6E-8954-0472AA41F675 at cerege.fr>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Jean-Michel,
>
> Thank you for your answer. I will take a look at these files, to see if it
> is feasible make such an ideal age tracer work with the dic pkg.
>
> I think that it would be really helpful to have this output to interpret
> changes in oxygen concentration in the ocean between different model runs.
>
> Cheers,
> Alexandre
>
>
> ------------------------------
>
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>
> End of MITgcm-support Digest, Vol 167, Issue 21
> ***********************************************
>

-- 
Hanut Vemulapalli
Btech Undergraduate
Aerospace Engineering
IIT-Madras
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