[MITgcm-support] potential density

[Martin Losch]

Bruno,

I do not think that we have a function for potential density anywhere in the model code. All computations of density are done with code for in-situ density, but this code is used to approximate a local potential density gradients by using pressure from a different level (usually on vertical grid point away), e.g. for compuations of drho/dz. For the horizontal derivatives I assume that the gradient computed from in-situ density is a good LOCAL approximation of the gradient from neutral density. So Matt is right.

about the diagnostics: WRHOMASS the vertical buoyancy flux: w*(rhoKm1+rhoK)*0.5 _d 0
where rhoKm1 is the "density of water at the level above (k-1), evaluated at pressure level k" (see diags_rho.F). U/VRHOMASS are u/v*rho*hFac with in-situ density.

Martin

On Mar 22, 2011, at 2:20 PM, Bruno Deremble wrote:

> Good morning,
> 
> In do_oceanic_phys, are sigmax and sigmay the gradients of potential density (as stated in the manual in the gmredi section)? I ask this because they are computed using 'rhoinsitu' which I presume is the in situ density and not the potential density.
> 
> in the diagnostic package WRHOMASS is associated to Vertical Transport of Potential Density whereas URHOMASS and VRHOMASS are the horizontal transport of density. Is it correct in both cases?
> 
> thank you
> bruno
> 
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