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What variable to use for diffusion flux?

juliettelavoie

Juliette Lavoie
New Member
Does DIA_IMPVF_TEMP (TEMP Flux Across Bottom Face from Diabatic Implicit Vertical Mixing) include all vertical diffusive flux in the ocean?

If yes, what is KPP_SRC_TEMP (TEMP tendency from KPP non-local mixing term) ? The diffusive flux calculated from KPP_SRC_TEMP seems very large.
 

klindsay

CSEG and Liaisons
Staff member
Juliette,

I apologize for the delay in your question getting answered.

DIA_IMPVF_TEMP only includes the tracer gradient dependent term of diabatic (cross-isopycnal) mixing.

KPP_SRC_TEMP arises from a term in the KPP vertical mixing scheme that is independent of tracer gradient. It is sometimes referred to as the non-local mixing term.

Please note that DIA_IMPVF_TEMP is a flux and KPP_SRC_TEMP is a tendency.

Note that eddy parameterization of the model's lateral diffusion scheme also has a vertical component, due to mixing along isopycnals and eddy induced flattening of isopycnals. The combined effect these processes is in the variable HDIFB_TEMP.

Keith
 

juliettelavoie

Juliette Lavoie
New Member
Thank you for your help Keith!

Just to confirm how the variables relate to equations.
In the pop reference manual, equation (7.66) (shown in picture) is D_v (\phi)= (\kappa(\phi_z - \gamma))_z.
where _z is a derivative in z.

Screen Shot 2020-11-17 at 4.33.48 PM.png

DIA_IMPVF_TEMP=\kappa \phi_z
and
KPP_SRC_TEMP=(-\kappa \gamma)_z.
where \phi is potential temperature.

so D_v = (DIA_IMPVF_TEMP)_z + KPP_SRC_TEMP ?


Also, HDIFB_TEMP is called a flux (TEMP Horizontal Diffusive Flux across Bottom Face). Why does it have unit of tendency ( degC/s)?
To get the tendency, should we do (HDIFB_TEMP)_z * \Delta z?
 
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