[MITgcm-devel] conservation Problem with KPP viscosity

[Jean-Michel Campin]

Hi, 

I checked-in the fix, added the new S/R to the list ad list,
but taf generates a lot of recomputations.
Patrick, when you have time, you will have to do something
with this. Sorry.

Jean-Michel

On Fri, May 04, 2007 at 12:09:34PM -0400, Jean-Michel Campin wrote:
> Hi Dimitris,
> 
> I have a temporary fix for this non-conservation problem,
> which consists in exchanging KPPviscAz after kpp_calc.
> 
> I think it would be good to sort out why this exch is needed, 
> and to fix it properly (in kpp_calc, something to do with the
> computational domain), but for now, I am thinking of checking-in 
> my fix (adding the exch call). OK like this ?
> 
> Jean-Michel
> 
> On Mon, Apr 30, 2007 at 04:58:14PM -0700, Dimitris Menemenlis wrote:
> > Jean-Michel, any more ideas about this KPP conservation problem.  From your 
> > description below it sounds like problem is not caused by KPP itself but by 
> > some inaccuracy with time-stepping scheme in the presence of large, 
> > spatially varying vertical viscosities ???
> > 
> > >Seems that the problem a conservation of T & S in the donuts
> > >is related to KPP viscosity:
> > >When I comment out CALL KPP_CALC_VISC in calc_viscosity.F,
> > >I get a good conservation of T (~1.e-5 J/m2) and S (~1.e-8 g/m2),
> > >over 1 year, which is what I expect given the machine precision.
> > >On the contrary, with KPP-viscosity on, the drift in T & S are
> > >still small ( ~1 J/m2 & ~1.e-5 g/m2) over the same period,
> > >but much larger than what they should be.
> > 
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