# [MITgcm-support] PH and PHRefC

Ryan Abernathey ryan.abernathey at gmail.com
Fri May 26 20:08:18 EDT 2017

Very useful! Thanks for sharing Jody!

Once I figured this out and wrote it down so I would remember it:
PHRefC = gravity * rhoref * RC[k]

On Fri, May 26, 2017 at 6:24 PM, Jody Klymak <jklymak at uvic.ca> wrote:

>
> Hi all,
>
> OK, about once a year I get re-confused about the meaning of the data
> contained in PH, PHL, and PHRefC.  I use a linear equation of state
> in z-coordinates with an oceanic buoyancy relation, so it should be pretty
> simple.
>
> One would think that to get the total pressure one would just add P = PH +
> PHRefC, but that is indeed not the case if tRef and/or sRef vary with depth
> (k).  PHRefC is simply g*Z (where Z is the z at the center of the cells).
> PH is the dynamic pressure: (1/rho_0) \int (rho-rho_{Ref}(z)) g dz.
> Nowhere, that I can tell, is the cumulative integral of rho_{Ref} stored
> (nor indeed tRef or sRef).
>
> My sleuthing, mainly so I don’t do this again (ha), but perhaps is useful
> to others, is at
>
> https://gist.github.com/jklymak/156c30b5344a9cf63e8aebc429fee1c6
>
> I do wonder why PHRefC doesn’t include the full reference pressure using
> tRef and sRef to calculate rhoRef: i.e. (1/rho_0) \int g rho_{Ref}(z) dz. I
> don’t need g*zc saved for any reason.  But maybe other co-ordinate systems
> or EOSs make sense of this variable?
>
> Thanks,   Jody
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