[MITgcm-support] On the use of PH and PHL reverse calculation of interface heights

[Martin Losch]

Hi Song,

I am not sure if I understand this correctly. In your model setup, do you use the nonlinear free surface, r-star coordinates, or anything like that?

If you do you could use the diagnostics UVELMASS and VVELMASS, which already contain the layer thickness; they are basically uVel*hFacW and vVel*hFacS. If you multply by drF, you’ll get the massflux per layer and can use for potential vorticity integrated over the layer, right?

PHL is the geopotential heigh anomaly at the bottom of the domain, not at the interface. PH (phiHyd) is the geopotential height anomaly at the cell centres (not the the interfaces)

Martin

> On 17. Oct 2021, at 15:31, 万松 <wansong at stu.ouc.edu.cn> wrote:
> 
> Hi，
> 
> I'm sorry to bother you with a small matter. I am using a two-layer model to calculate the potential vorticity and need to get the thickness of each layer. Now I try to use PH and PHL to invert the interface fluctuation of the upper and lower layers:
> PHL=g*Eta+ (rho - rho_const)*g*(z+Depth)/rho_const
> Here, z is the interface. However, the values of PHL and g*Eta are so close that the resulting z is almost equal to Depth. Did I misunderstand PHL?
> -Thanks for much，
> Song
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