[MITgcm-support] consult

[Martin Losch]

Hi,

in case no-one has given you an answer:
Please change your monitorFreq=1.0 and then have a look at the standard 
output. You'll find, that the parameters dynstat_advcfl_uVel/vVel/wVel 
(probably wVel) will become large even before rhsMax. My guess is that 
you are violating the CFL (Courant-Friedrich-Levy, spelling?) stability 
criterion, when you decrease the delX/Y/Z. The CFL criterion is a very 
basic stability criterion, so to speak the necessary condition for 
numerical stability in any explicit time stepping scheme, and says that 
u*deltaT/delX (and  v*deltaT/delY and w*deltaT/delZ) must be smaller 
that .5 or so. So that means you'll have to decrease your time step 
until this criterion is satified. Start with a small value for deltaT, 
say 10.0 seconds, and then increase it just to the point where it 
explodes again.

Good luck,
Martin


On Monday, January 5, 2004, at 10:30  AM, Zhaipu Ma wrote:

> Dear Sir,
> I adapt the /exp4/, but the delZ is much smaller than delX and delY.
> My data is delX=DelY=9260m, and delZ=3m~10m,  say delZ=6.5m,
> no change for the other parameters, the MIT runs for nearly 4000 
> iterations,
> if  delZ=10m,then MIT runs 5722 iterations, if delZ=15,then much more 
> iterations reached.
> I check the MIT, it says that rhsMax>=1.0e200, than comes a NAN,
> So, for such condition, how can I adjust the delZ?
> Because I want to calculate the shelf sea. The Max depth is 65m 
> (bottom),
> each layer is 3,3,3,3,3,3,5,5,10,17m,
>  I can not adapt delZ to 20m, it's too coarse for such a depth
> how to give the parameter for such a thin layer ?
>
> Best  regards.
> mazhaipu
> Jan,5th,2004.
>
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>
Martin Losch // mailto:mlosch at awi-bremerhaven.de
Alfred-Wegener-Institut für Polar- und Meeresforschung
Postfach 120161, 27515 Bremerhaven, Germany
Tel./Fax: ++49(471)4831-1872
http://www.awi-bremerhaven.de/People/show?mlosch