[MITgcm-support] model resolution

[Martin Losch]

Hi Neil,

as I wrote yesterday, I recommend using viscAhGrid instead of viscAh, you might even want to consider using the Leith viscosity scheme (see <http://mitgcm.org/public/r2_manual/latest/online_documents/node85.html>, especially the subsections).

Are you familiar with asynchronos time stepping/tracer acceleration? if not, I suggest that you read about it (e.g. Bryan 1972, Danabasoglu 2004). 

Ideally you just use one time step (parameter deltaT) in data, but for spin-up, it is "allowed" to have longer time steps for tracers (trial and error, I am afraid, but the larger the ratio of deltaTtracer/deltaTmom, the more physical distortions you'll get). Often, the first couple of days require a shorter time for momentum, because of fast initial adjustment processes and later slightly longer steps can be used.

Martin

On Jul 3, 2013, at 12:32 AM, Neil Patel <nigellius at gmail.com> wrote:

> Sorry for the question before, I think I found the answer to it here:
> 
> http://mitgcm.org/public/r2_manual/latest/online_documents/node131.html
> 
> I had missed that section. So for viscAh, I just need it large enough so that the Munk layer width in equation 3.43 (from the link) is bigger than the width of the largest grid cell. What affects what the best choice for a thermodynamic time step? And for the momentum time step, small enough so it doesn't crash?
> 
> Thanks,
> 
> Neil
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support