Re:_[MITgcm-support]_Orlanski_and_mass_conservation

[samar khatiwala]

On Mon, 2 Aug 2004, Petter Stenström wrote:

> With Samar's permission I can send you his code and my additions.
>

Hi Petter, feel free to distribute my code!

Samar

> ------- Original message -------
> From: spk at ldeo.columbia.edu
> Date: Mon, 2 Aug 2004 10:41:16 -0400 (EDT)
>
> Hi Stefano
>
> I may be wrong here, and its been ages since I worked with the
> obcs package, but mass conservation was one of problems I
> encountered when I first wrote this package. (Both Sonya Legg
> and Jake Gebbie are more current with this package and may have
> different experiences to report.) In my simulations,
> there was a mean flow in the problem and this had to be accounted
> for in computing OBEu etc. I don't know the details of your experiment,
> but in my problem the OBCS were applied to the "wave" part of the
> flow, i.e., deviations from a vertical average. To implement this,
> in say orlanski_east, I have code like:
>
> ...
>                OBEu(J,K,bi,bj) = ubarnew + uWave
> C--------------Average uWave vertically---------
>                xArea =
>      &           _dyG(I_obc,J,bi,bj)*drF(K)*_hFacW(I_obc,J,K,bi,bj)
>                uWaveAvg(J) = uWaveAvg(J) + uWave*xArea
>                xAsum(J) = xAsum(J) + xArea
> C-----------------------------------------------
> ...
> C     Subtract vertical average of uWave
>       DO J=1-Oly,sNy+Oly
>          I_obc=OB_Ie(J,bi,bj)
>          IF (I_obc.ne.0) THEN
>             uWaveAvg(J)=uWaveAvg(J)/xAsum(J)
>          ENDIF
>       ENDDO
>       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) = OBEu(J,K,bi,bj) - uWaveAvg(J)
>             ENDIF
>          ENDDO
>       ENDDO
>
> Perhaps you may have to do something similar.
>
> Samar
>
> On Mon, 2 Aug 2004, Stefano Querin wrote:
>
> > Hi,
> > I am making some tests using the Orlanski OBCs. I recently observed that
> when a non-negligible velocity field reaches the OB, the mass conservation
> in the domain is no longer satisfied.
> > For example, in the Plume on slope verification experiment, when the
> plume reaches the boundary, there is a volume increase in the basin (eta
> reaches 180 m in few days!). In this case, I simply made a longer run to
> see the evolution of the plume for some more days.
> > I observed similar problems even when I used the flag: exactConserv=.TRUE.
> > To be more clear I attach three pictures showing the problem:
> > the first two show the evolution of eta and u-velocity (varying with
> depth) in time, the third is a sketch of the temperature profile when the
> plume "reaches" the OB (after 2.5 days; the horizontal lenghtscale is of
> tens of meters).
> > My questions are:
> > - (first of all!) did I make some mistakes?
> > - is there a way to control the mass fluxes in the domain (in the
> orlanski_east(north, south, west).F routines there is no mention to eta)?
> > - if I impose the Orlanski condition on the eastern boundary (as
> prescribed in data.obcs), do I (implicitly) impose the same condition on
> the western OB (u-velocity is non zero on that OB)?
> > Thank you very much for any suggestion.
> >
> > Sincerely,
> >
> > Stefano Querin
> >
> > P.S.: (for Patrick) any news about the active OBCs?
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