[MITgcm-support] semi-prognostic calculation with MITgcm

[Samar Khatiwala]

Hi Chris,

Great idea! This could work. 

You mentioned using pkg/rbcs to impose, say, monthly mean (or other time-varying) hydrographic T/S. 
However, if I set set temp/saltStepping to false, rbcs won't be called, right? e.g., I have the following sequence 
of calls:  S/R THERMODYNAMICS -> CALC_GT -> EXTERNAL_FORCING_T -> RBCS_ADD_TENDENCY
But CALC_GT is only called if tempStepping is true.

I suppose I could hack the code and replace model T/S with my own T/S. S/R WRITE_STATE seems like a safe 
place to do this.

Thanks!

Samar

On Apr 10, 2010, at 8:28 AM, Chris Hill wrote:

> Samar,
> 
> I think one way to do this is to
> 
> (1) set saltStepping, tempStepping false
> (2) Have some initial T and S that are the external hydrography.
> (3) add two "passive" tracers that represent the transported T and S
>      and that are forced however you want.
> 
> The passive tracers can have GM, Redi, can mix convectively and according to
> boundary layer schemes like KPP, can have advection options etc....
> just like T and S
> - but they won't change the hydrography.
> If you want the hydrography T/S to vary according to some imposed form, then
> you can  add rbcs bits to do that.
> Main thing to watch out for would be making sure hydrographic T/S are
> statically stable.
> If they a unstable, convective mixing there will be continuous for
> the tracers  - since I don't think
> the hydrographic T/S will get homogenized.
> 
> Chris
> 
> On Sat, Apr 10, 2010 at 1:20 AM, Samar Khatiwala <spk at ldeo.columbia.edu> wrote:
>> Hello,
>> 
>> Has anyone implemented/carried out a 'semi-prognostic' calculation with MITgcm? This is where you replace
>> the model density (T/S) in the hydrostatic balance with an externally prescribed field, or a weighted average of the
>> externally prescribed and model density field. The tracer equations are left unchanged.
>> 
>> If someone had done this and can share their model mods with me, that would be fantastic. Any hints on how best to
>> implement this would also be welcome. It wasn't entirely obvious which routine(s) to change. Is S/R CALC_PHI_HYD
>> the one to change?
>> 
>> Thanks very much,
>> 
>> Samar
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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> 
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