[MITgcm-devel] Re: KPP subgrid-scale mixing

[Martin Losch]

Are An and Michael on the devel-list? I don't know, so I'll include  
them in the address list, sorry for multiple mails.

Thanks for putting a finger on yet another sore spot of my wish-to-do  
list (o:
Andrea and I have a pretty clear idea how to start and investigate  
this issue and implement a scheme that may or may not improve the  
subgrid-scale surface boundary conditions (heterogeneous boundary  
conditions). I'd really like to get ahead with this, but alas, there  
has not been time for this yet.

Dimitris, I admire your optimism that something like a sub-grid scale  
mixing scheme would fix any serious problems of a global high  
resolution simulation. My personal opinion is that these things are  
rather something for really coarse models (1deg and coarser), but  
hopefully we'll soon be able to find out ...

Martin

On 19 Jul 2007, at 20:30, Dimitris Menemenlis wrote:

> Hi Andrea, I am moving discussion to MITgcm-Devel list.
>
> I think that there is definitely an impetus to do something about  
> representation of convection due to salt rejection under sea ice.   
> I suspect that treatment of salt rejection may in part be  
> responsible for CS510 solution problems both in the Arctic and in  
> the Southern Ocean.
>
> As a possible alternative (or temporary fix) to a full blown KPP- 
> sub-grid-scale parameterization, I could implement the salt  
> rejection scheme of Duffy, Eby, and Weaver (GRL 1999, vol 26, pages  
> 1739-1742).  This scheme adds "saltFlux" into several layers at the  
> same time, rather than in the surface level only, based on a  
> density-difference criterion.  It is similar in some ways to the  
> way shortwave radiation is currently treated but without the  
> exponential decay.
>
> Does anyone on the devel list have experience with the Duffy et al.  
> scheme or alternative suggestions?
>
> Dimitris
>
>
>> hi dimitris,
>>> Hi Andrea, I am wondering whether you did pursue your KPP sub- 
>>> grid scale mixing idea?  An Nguyen and I are seeing some issues  
>>> with salt rejection by sea ice that may possibly be helped by a  
>>> subgrid scale convection parameterization of the type you  
>>> described when we last spoke.  Cheers, Dimitris
>> the short answer is 'no'.
>> (now you can stop reading if you want....)
>> the long answer is that i started to set stuff up to do it,
>> and what i did to the code broke taff big time. so j-m came behind
>> me and took it all out..... but martin and i did discuss this at  
>> some length, and the strategy for doing this was mapped out. we just
>> never pursued it. is there an impetus to pick it up again? (i have
>> cc'd martin on this to see if he has any thoughts?)
>> take care,
>> andrea