[MITgcm-support] Re: nonHydrostatic

[Christopher L. Wolfe]

> is interesting that with a flat bottom nothing happens --- I have  
> also verified that in the small 20x16x23, 2-deg lab_sea domain ---  
> but that once you add bathymetry, even with a stable temperature  
> profile and with uniform salinity, things start moving  
> spontaneously.  Would such a behavior be expected in real ocean or  
> is it just numerical artifact?  D.

Dimitris,

This behavior is entirely physical, but I wouldn't expect to see it  
in the real ocean. Even if you start out with a stable  
stratification, there's going to be diffusive fluxes as the system  
tries to adjust to a uniform temperature. If the bottom is flat then  
the bottom boundary condition is horizontally uniform and the density  
remains horizontally uniform throughout the adjustment process. With  
topography, location of the bottom boundary condition is no longer  
horizontally uniform, so horizontal density gradients develop and the  
velocity becomes non-zero.

Also, if your topography pokes up into a region of strong  
stratification, there's going to be some rapid local adjustment to  
satisfy the bottom boundary condition T_z = 0, which will likely  
create horizontal inhomogeneities in the temperature field, leading  
to flow.

This shouldn't have anything to do with whether the model is  
hydrostatic or not, although the details of the adjustment might.

Christopher

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Dr. Christopher L. Wolfe                   858-534-4560
Physical Oceanography Research Division    OAR 357
Scripps Institution of Oceanography, UCSD  clwolfe at ucsd.edu
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