[MITgcm-support] question about convection in nonhydrostatic and hydrostatic

[Martin Losch]

Hi Ping,

the non-hydrostatic dynamics by themselves don't "do" anything. I like to see it the other way around: Once you resolve convective scales (order 100m and less), ie. when you grid spacing is very fine, you need to turn on the non-hydrostatic dynamics, because the flow is now long hydrostatic, also for numerical reasons (you get "grid cell storms" in very high resolution hydrostatic models).

This means that even with non-hydrostatic dynamics, you can have a convection scheme turned (ivdc_kappa = "some value", I think 1000 is way to large, is only one option, btw), but you may not want to because resolve the convection explicitly. If you need to parameterize the convection, you should evaluate if you need the expensive non-hydrostatic dynamcs at all.

Martin

On Nov 16, 2013, at 4:44 PM, Ping Zhai <pingzhai at MIT.EDU> wrote:

> Hi,
> I am confused about the convection parameterization in a nonhydrostatic model.
> I know that in the hydrostatic option, the convection can be parameterized by setting ivdc_kappa=1000 (or other value) when the stratification is unstable.
> Do I need to set ivdc_kappa in nonhydrostatic option? Does nohydrostatic model resolve the convection so that we don't need to parameterize convection as in hydrostatic model? If I set ivdc_kappa=1000 in a nonhydrostatic model, does it conflict with the model?
> Best,
> Ping
> 
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