[MITgcm-support] SSH drift and obcs again

[Martin Losch]

Hi Tom,

I'm glad that exp4 has no significant drift in Eta, it shouldn't 
because the specified flow is exactly balanced (25cm/s zonal velocity 
everywhere). At least this part of the code works.

I ran the experiment for 10 timesteps, and yes, at the beginning 
min/max Eta is +/-4.87m, but at timestep 5 this has already reduced to 
0.5m. The initital shock of suddenly having u=25cm/s at the boundary is 
probably a bit much. You could probably get rid of that by specifying a 
better initial flow field (better than zero) with uVelInitFile or 
whatever it is called.
I added a meridional component by:
  OBNuFile = 'OBmeridU.bin',
  OBSuFile = 'OBmeridU.bin',
  OBWuFile = 'OBzonalU.bin',
  OBEuFile = 'OBzonalU.bin',
in data.obcs (so same velocities, so that now the flow is diagonal 
through the domain), and the solution changes accordingly (Eta is 
different by +/-50cm).

to me, everything looks OK. Alistair suggests to include topography, 
but there is already a Gaussian bump in the domain. Maybe Alistair 
means topography along the open boudnaries?

Martin

On Nov 7, 2005, at 11:33 PM, Thomas Haine wrote:

> Hi Martin,
>
> I'm confused. exp4 has zero eta drift in the standard configuration in
> the latest code. The cg2d rhs is also very near zero. Yet there is
> normal flow through the domain. If I add a meridional component to the
> normal flow the results are, essentially, the same.
>
> Also, (max, min) eta is +/-10m after 1 step. Is this correct?
>
> So, I can't reproduce the problem I've seen in exp4 and I don't know
> why.
>
> Tom.
>
>
> On Mon, 2005-10-31 at 08:58 +0100, Martin Losch wrote:
>> Hi Tom,
>>
>> no final ideas, but do you think you can reproduce your problem based
>> on exp4 in the current code (four open boundary conditions with
>> topography in the middle of the domain)? If so, could you send me the
>> code modifications that are necessary for this? This would let me try 
>> a
>> few things myself (not that I think that I will come up with something
>> spectacular, but as I wrote earlier, I should probably look into that
>> problem for my application).
>>
>> Martin
>
> -- 
> --------------------------------------------
>  Thomas W. N. Haine
>
>  Associate Professor of Physical Oceanography,
>  Department of Earth & Planetary Sciences,
>  329 Olin Hall, The Johns Hopkins University,
>  Baltimore, MD 21218, USA.
>  Tel : 410 516 7048,   Fax : 410 516 7933
>  Thomas.Haine at jhu.edu
>  http://www.jhu.edu/~eps/faculty/haine
> --------------------------------------------
>
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