[MITgcm-support] only eta as open boundary ?

[Martin Losch]

Kaveh,

you probably use a linear free surface in your model configuration? With a ***linear*** free surface, the open boundary conditions for Eta have no effect (basically, there are none to be specified). But your method of converting the elevation into bartropic velocities seems to work, doesn’t it?

Otherwise you need to use a non-linear free surface, which will make the experiment more complicated.

Martin

> On 30 Jan 2016, at 20:50, kaveh Purkiani <kavehpurkiani at googlemail.com> wrote:
> 
> Hi MITgcm users,
> 
> I have been trying to use eta as the only boundary condition in 
> a configuration.
> 
> below you see the relative part of configuration regarding the bcs at data and data.obcs
> 
> data
> 
>  periodicExternalForcing=.TRUE.,
>  externForcingPeriod=900.,
>  externForcingCycle =43200.,
>  &
> 
> 
> data.obcs
> 
>  OBCSfixTopo=.FALSE.,
>  OB_Jnorth= 80*-1,
>  OB_Jsouth= 80*1,
>  OB_Ieast = 42*-1,
>  OB_Iwest = 42*1,
>  useOBCSprescribe = .TRUE.,
> 
>  OBNetaFile = 'OBNeta.bin', (Nx,time)
>  OBSetaFile = 'OBSeta.bin', (Nx,time)  
>  OBWetaFile = 'OBWeta.bin', (Ny,time)
>  OBEetaFile = 'OBEeta.bin', (Ny,time)
> 
> The boundary conditions are obviously read in (only at boundaries output shows identical to what is prescribed as boundary condition),
>  but they are not applied inside the domain. Except the boundaries, rest of the domain does not show any elevation.
> 
> When I convert the sea surface elevation (eta) into barotropic velocity and prescribe the OB(N,S,E,W)(u,v) and no elevation at boundaries, it works
> properly, with meaningful eta, zonal and meridional values.
> 
> I appreciate any suggestions.
> 
> regards,
> 
> Kaveh. 
> 
> 
> 
> 
> 
> 
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