[MITgcm-support] pressure from MITgcm

[Ed Hill]

On Fri, 2005-11-18 at 15:32 -0500, Sergey Vinogradov wrote:
> Hi folks!
> 
> Did anyone compare the pressure profiles computed from hydrostatic 
> anomaly ('PH' output) and from density?  
> I'm using atm. loading with MITgcm. In order to compute the full 
> pressure at the center of k-th layer, I can either get it from T and S 
> through density: p (rho) = rho0*g*eta + g* J (rho*dz), or, use the PH 
> output (phiHydC variable), which, according to previous correspondence 
> with Martin and Dimitris, can also give me the full pressure (at k-th 
> layer):
> p (PH) = rhoConst*PH(k) + g*rhoConst*D(k)
> Notations are: rho0 - surface density; g-gravity; eta-full sea-surface 
> elevation; dz-layer thicknesses; rhoConst - reference density; D - 
> central depths of layers; J - integral from cell center depth to the 
> surface.
> I get different variability from these two methods (see attached 
> fragment of timeseries sampled at some layer). Other than the difference 
> in eos that I use for density computations, what may be the reason for 
> discrepancy in the variability between these two pressure computations? 
> Am I missing something?

Hi Sergey,

This is just a guess but are you using z* coordinates?  If so, you'll
need to take into account the time-varying thicknesses of all the
layers:  thickness at center = hFacC * dz

Ed

-- 
Edward H. Hill III, PhD
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