[MITgcm-support] Bottom Pressure nonhydrostatic
Martin.Losch at awi.de
Thu Oct 15 14:58:19 EDT 2009
this is a tricky question, and I thought that I knew the answer, but
after having a closer look at the code I realized that I no longer
understand this business, but I know this much:
in z-coordinates PHL, is the the pressure anomaly divided by rhoConst
at the bottom of the domain. It's a pure diagnostics, and it's
computed in model/src/diags_phi_rlow.F
It's an (potential) anomaly and to get the total hydrostatic phiHyd,
you need to add that contant part gravity*abs(z).
Then in some cases you need to add the surface contribution as in
totPhiHyd (diags_phi_hyd.F: Bo_surf*etaN+phi0surf, Bo_surf = gravity
in z-coordinates, see ini_linear_phisurf.F), but I ran across a place
(calc_phi_hyd.F) where (for a nonlinear free surface and if
select_rStar.EQ.0 .AND. nonlinFreeSurf.GT.3)
surfPhiFac*etaH(i,j,bi,bj) is added to the surface value of phiHyd).
That's most likely correct, but I don't know why. Maybe Jean-Michel
has a simle explanation (probably has to do with time stepping and the
pressure being updated at a different time than etaH and etaN).
The non-hydrostatic pressure is completely separate and is never part
of PHL nore phiHyd (which as the name implies is completely
On Oct 14, 2009, at 6:35 PM, David Hebert wrote:
> In grepping the code (DYNVARS.h specifically) it looks like PHL is
> the bottom hydrostatic pressure. Two question about this..
> 1) Does this include surface contribution (as specified for
> totPhiHyd in DYNVARS.h)
> 2) In a nonhydrostatic simulation would I obtain bottom pressure as
> PHL + PNH(bottom)?
> Or do I need to use
> PH(bottom) + PNH(bottom)?
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
More information about the MITgcm-support