[MITgcm-support] Anamalous Decrease in Sea Surface Level and SPONGE Layer

[Himansu Pradhan]

Sorry for a belated answer.

i too also confused why i am LOOSING sea level. Except the values for "Eta"
i am getting a good circulation , temperature and salinity fields using
Orlanski boundary condition.

i am attaching my "input" and "code" directory for checking and suggesting
me anything to move forward.

I am trying the suggestation regarding SPONGE layer.

Thank you



On Thu, Sep 20, 2012 at 10:51 PM, Jody Klymak <jklymak at uvic.ca> wrote:

>
> Himansu,
>
> Not sure why you are losing sea level...
>
> For a sponge, you need the spatial extent to be at least a large fraction
> of a mode-1 tidal wavelength.  Unless you are in shallow water, 40 km is
> not going to do it.  Second, your time constants are far too long to absorb
> internal waves.  They will bounce off that boundary no problem.  Use
> timescales that are closer to an hour at the outer boundary and 12 h at the
> inner side.
>
> I do something like
>
> # Sponge layer parameters
>  &OBCS_PARM03
>  Urelaxobcsinner=500.,
>  Urelaxobcsbound=500.,
>  Vrelaxobcsinner=500.0,
>  Vrelaxobcsbound=500.0,
>  spongeThickness=10,
>  /
>
> but my sponge is closer to 150 km wide because I telescope the grid on the
> boundaries.
>
> Cheers,    Jody
>
> On Sep 20, 2012, at  9:44 AM, Himansu Pradhan wrote:
>
> > Hello MITgcm users,
> >
> > I have configured MITgcm for my region (174*200*17) to look after
> circulation and internal waves. dx = 2.5 km and dy = 2.5km approximatly .
> Tides are included  into the  region through momenteum equations to take
> note of the thermal/density oscillations. Orlanski OBC were applied at the
> boundary to take care for physics/dynamics.
> > ... here starts the PROBLEM ???? their is an ANAMALOUS DECREASE in the
> Sea Surface Level with time. ?????
> > .
> >  so finding myself NOWHERE i wanted to include SPONGE layer at the
> BOUNDARY .------> Is this OK ??? .( need some suggestation/help HERE ).
> >
> > to proceed with I included :
> > #define ALLOW_OBCS_SPONGE   : ---> in ..../code/OBCS_OPTIONS.h
> >
> > and edited "data.obcs" :
> > # Open-boundaries
> >  &OBCS_PARM01
> >  OBCSfixTopo=.FALSE.,
> >  OB_Jnorth=174*-1,
> >  OB_Jsouth=174*1,
> >  OB_Ieast=200*-1,
> >  OB_Iwest=200*1,
> > # useOrlanskiN/S/E/S=.FALSE.,
> >  useOBCSbalance=.FALSE.,
> >  useOBCSprescribe = .FALSE.,
> >  useOBCSsponge=.TRUE.,
> >  &
> > # Orlanski parameters
> >  &OBCS_PARM02
> >  Cmax=0.45,
> >  cVelTimeScale=1000.,
> >  &
> > # Sponge-layer parameters
> >  &OBCS_PARM03
> >  Urelaxobcsinner=864000,
> >  Urelaxobcsbound=43200,
> >  Vrelaxobcsinner=864000,
> >  Vrelaxobcsbound=43200,
> >  spongeThickness=15,
> >  &
> >
> > to start with. i had given : " # Sponge-layer parameters ;  &OBCS_PARM03
> " .  values BLINDLY. it didn't HELP. The temperature and Circulation
> results were not satisfactory.
> >
> > I have gone trough the manual , . But need a bit more explanation
> regarding the physics of these paramaters.
> >
> > And supposingly if i want to run MITgcm with this current configuration
> for one month, ????? what should be the VALUES (of Sponge-layer parameters)
> to START with. ??????
> >
> > Any Suggestation/Help is highly appreciated.
> >
> > Thanking all in advance.
> >
> > Himansu.
> >
> >
> >
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
>
> --
> Jody Klymak
> http://web.uvic.ca/~jklymak/
>
>
>
>
>
> _______________________________________________
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> MITgcm-support at mitgcm.org
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>
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