[MITgcm-support] Fwd: boundary conditions and biharmonic damping

Ed Hill ed at eh3.com
Fri Feb 18 08:05:47 EST 2005

> -------- Forwarded Message --------
> > From: Joseph LaCasce <josephhl at met.no>
> > To: mitgcm-support at mitgcm.org
> > Subject: boundary conditions and biharmonic damping
> > Date: Fri, 18 Feb 2005 13:50:26 +0100
> >  Hello! Goran Brostrom has been running some idealized ocean 
> > experiments with a square basin and thermal relaxtion at the 
> > surface, but without winds (and no salinity). We've noticed 
> > the model develops a very sharp temperature gradient next to 
> > the eastern wall when using biharmonic mixing for temperature. 
> > I looked through the documentation but couldn't find anything 
> > specific about the boundary conditions with biharmonic 
> > diffusion. But it looks like the sharp gradient (which 
> > exists between the wall and the first grid point) is counter 
> > to a zero heat flux requirement there. The strong gradient 
> > leads to a significant Veronis effect, brought about the 
> > biharmonic term (I believe)---you see strong sinking, all 
> > the way to the bottom, with upwelling occurring at the next 
> > grid point into the interior. Any infor- mation about the 
> > lateral boundary conditions would be appreciated! As I 
> > understand it, the biharmonic mixing is not rotated (along 
> > isopycnals). Is that incorrect? regards---- Joe LaCasce

Hi Joe,

I've subscribed you to the list and forwarded your message.

Hopefully someone else (perhaps Alistair?) will be able to answer your
bc/viscosity question!


Edward H. Hill III, PhD
office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
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