[MITgcm-support] diagnosing gmredi fluxes for tracers

[Jean-Michel Campin]

Hi Christoph,

There are ways to get diagnostics for some of the different pieces of GM-Redi.
But it would help if we know what parameter you are using (from data.gmredi)
and if you are using implicitDiffusion=.TRUE., (from main paramter file "data").

The fact that you have:
> #define GM_BOLUS_ADVEC
> in GMREDI_OPTIONS.h.
does not mean that you are using the advective form (it's just that the 
code is compiled, and you can use it or not).

Cheers,
Jean-Michel

On Mon, Oct 28, 2013 at 11:34:05PM +0100, Christoph Voelker wrote:
> Dear MITgcm'ers,
> 
> I have a run of a biogeochemical model (i.e. with several additional
> passive tracers) and I am trying to diagnose (and hopefully understand)
> what the GMREDI eddy parameterization contributes to my tracer fluxes.
> In doing so I got somewhat confused my the many options and parameter
> settings that are possible in that package; I found it hard to follow
> how the advective and diffusive fluxes are really calculated.
> 
> My settings include
> #define GM_VISBECK_VARIABLE_K
> #define GM_BOLUS_ADVEC
> in GMREDI_OPTIONS.h.
> so, I am using the bolus velocity form, not the skew flux form, with
> variable kappa_GM, a la Visbeck et al. '97. In addition I am using the
> Large, Danabasoglu, Doney tapering scheme. 
> 
> My questions concern the diagnostics associated with the tracer fluxes.
> 
> - Firstly, I assume that the explicit diffusive terms like DFrETr01
> contain the Redi isopycnal diffusion, perhaps plus the additional
> diffusion induced e.g. by the KPP sheme that I am using. Is this right?
> 
> - Secondly, is the bolus advective flux part of the advective flux
> diagnostics, like ADVrTr01? Or is this only the non-bolus advection?
> 
> - And finally, is there a way to diagnose the advective tracer fluxes
> from the bolus velocity alone, i.e. separate it from the background
> velocity advection, in a diagnostic variable, or does one have to write
> out the bolus stream function terms GM_PsiX and GM_PsiY, and then
> compute the induced additional advection offline?
> 
> Sorry if my questions are daft, but I really first tried to understand
> all this from the code,
> 
> Thanks, Christoph
> 
> -- 
> Christoph Voelker
> Alfred Wegener Institute for Polar and Marine Research
> Am Handelshafen 12
> 27570 Bremerhaven, Germany
> e: Christoph.Voelker at awi.de
> t: +49 471 4831 1848
> 
> 
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