[MITgcm-support] advective and diffusive diagnostics

[Patrick Heimbach]

To add to Baylor's description at the thread
http://forge.csail.mit.edu/pipermail/mitgcm-support/2007-February/ 
004605.html

Quoting:
1) UVELTH is just the correlation between U and T.
2) UTHMASS is the correlation between U and T, weighted by 'mass', or
HFac, which gives free-surface corrections.
3) ADVx_TH is the 'effect of advection'.  It includes flux-limiting
and diffusion from the numerical scheme.

there is a fourth diagnostic
4) DFxE_TH
which could be termed "diffusive", i.e. it contains all
non-advective components in the dT/dt sum, such as diffusion due to
Laplacian or biharmonic diffusion (diffKh, diffK4) and due to GM/Redi.

The fields 3) and 4) (ADVx_TH, DFxE_TH) are mass-weighted as well
(yes, it's the mass of water in the grid cell),
so you don't have to worry about cell area, thickness or surface  
corrections
when computing sums or budgets.


-p.



On Mar 1, 2007, at 1:54 PM, Valerie Benesh wrote:

> I am currently trying to understand the units of the advective and  
> diffusive fluxes in the available diagnostics.  What is the  
> difference between mass-weighted transport of a tracer and the  
> advective flux of the tracer?  Does the mass transport include  
> diffusion? I take it mass-weighting involves the mass of water in  
> the grid cell?   How exactly are the units (kg/kg)*(m/s) come by  
> for mass-weighted transport?  How are the units (kg/kg)*(m^3/s)  
> achieved for fluxes of the tracer?  Are these the fluxes themselves  
> at each cell boundary?  Any help understanding these units is  
> appreciated.  Thanks,
>
> Val
>
>
>
> ***************************************************
> Val Bennington
> Graduate Student
> Atmospheric and Oceanic Sciences
> University of Wisconsin-Madison
> benesh at wisc.edu
> ***************************************************
>
>
>
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---
Dr Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
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