[MITgcm-devel] spurious vertical diffusion

[Martin Losch]

I agree with Chris, KPP is most likely the culprit. Try using simple  
convective adjustment instead of KPP and see what happens.

I have used advScheme = 7 (DST7 with flux limiter, require OLx=OLy=4)  
successfully.

The diagnostics are called
DFrI_TH and DFrE_TH for theta and diffusion (including KPP), but you  
want
ADVr_TH (the total vertical advective flux including numerical  
diffusion) minus WTHMASS (vertical flux of theta = w*theta), right?


Martin

On 8 May 2007, at 02:06, chris hill wrote:

> D.,
>
>  Have you tried putting in a tracer that is horizontally uniform  
> but that has a vertical profile? KPP will probably be doing  
> something gross, so the background diffusivity may not be so  
> relevant just below the ice.
>
> Chris
> Dimitris Menemenlis wrote:
>> Alistair and Jean Michel, are any of your super-duper new tracer- 
>> advection schemes ready for prime time on the cube?
>> In the Arctic domain of the 18-km cube configuration, there seems  
>> to be too much vertical diffusion (or perhaps horizontal diffusion  
>> across sloping isopycnals).  We have started an integration where  
>> the explicit background vertical diffusion is much reduced (from  
>> 1.4e-5 to 1e-6 m^2/s) but that does not seem to impact the  
>> solutions very much.
>> Right now we use
>>  tempAdvScheme=33,
>>  saltAdvScheme=33,
>> and we have zero explicit horizontal diffusivity.
>> Two specific questions:
>> 1) Is there a way to diagnose what is the effective vertical  
>> diffusivity in the integration?
>> 2) Is there an advection scheme that will lead to less spurious  
>> vertical diffusion than flux-limited DST3?
>> Dimitris
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