[MITgcm-support] Unstability in a Model (SOLUTION IS HEADING OUT OF BOUNDS)

[Martin Losch]

Hi,

looks like your configuration is not stable.
For debugging your configuration it’s always a good idea to set monitorFreq to deltaT (or smaller) in oder to get output every time step. You can then use this output to get a few hints about your problem. The model computes the maximum Courant numbers (advcfl_u/v/wvel_max) and all sorts of other things. 
There are a couple of  stability parameters that need to be satisfied. Some of them are listed in the tutorials, e.g. here <http://mitgcm.org/public/r2_manual/latest/online_documents/node115.html#SECTION00492100000000000000>
or here
<http://mitgcm.org/public/r2_manual/latest/online_documents/node131.html#SECTION004122100000000000000>

you can choose your parameters to satisfy these criteria. 
Initial conditions can be a problem, if they lead to a very strong initial adjustments (for example, strong gradients in the initial fields)

Martin

> On 19 Dec 2016, at 12:09, Bahman Alavi <bahman.al at gmail.com> wrote:
> 
> Hi all
> I configured a case in MITgcm, which happened to be perhaps unstable. I have tried to decrease the timestep, but it could not help and the error shows up at nearly same time (timestep X Iter).
> I also tried changing the "viscAh" and "tALPHA" but it didn't help. So I changed the "monitorFreq" to something over the final time, it results to "NaN" data.
> I have two questions according to what I said above:
> 1- Is my case unstable?
> 2- how can i know that my input data could be create this situation.
> Thanks
> 
> The error is:
> SOLUTION IS HEADING OUT OF BOUNDS: tMin,tMax= -1.238E+02  8.877E+02
>   exceeds allowed range (monSolutionMaxRange=  1.000E+03)
> 
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