[MITgcm-support] the implicit pressure components of PHIHYD?

[秋菊陳]

Hi Martin,

Thanks for pointing out diags_phi_hyd.F for me to start.
I believe I am still confused with the difference of totPhiHyd between r
and r* coordinates.

With your kind comments and the help page (2.10.2.1. Pressure/geo-potential
and free surface
<https://mitgcm.readthedocs.io/en/latest/algorithm/nonlinear-freesurf.html>),
I could understand the top part (line 62) of diags_phi_hyd.F.
Could you please have a look at my interpretation? Is that correct?

(if only consider first grid,)
help.page:
PHI = PHI_reference.state [ g*rho_const*abs(z1) ]
       + PHI' [ totPhiHyd ]
& PHI' = PHI_s [ g*eta ]                   <--> could be considered as
barotropic pressure/rho_const?
           + PHI'_hyd [ g*(rho1-rho_const)*abs(z1)/rho_const ]  <-->
baroclinic pressure/rho_const?

line 62:
totPhiHyd(i,j,k,bi,bj)            <--> PHI'
       = phiHydC(i,j)              <--> PHI'_hyd
       + Bo_surf(i,j,bi,bj)*etaN(i,j,bi,bj)    <--> PHI_s
       + phi0surf(i,j,bi,bj)          <--> EXFpress

that is,
geo-potential f(x,y,z) = reference state f(z) + barotropic part f(x,y) +
baroclinic part f(x,y,z) + other surface terms
Now I guess the ECCO variable PHIHYD I plotted could probably be the
baroclinic part only. (?)


The next part, line 107, is it physically the same as totPhiHyd in line 62,
but only in r* coordinate?
The value of line 62 should be the same as line 107?
Why does the reference state come into the equation?

dPhiRef =( Ro_surf(i,j,bi,bj)-rC(k) )*gravity            <-->
PHI_reference.state
 totPhiHyd(i,j,k,bi,bj)
      = phiHydC(i,j)*rStarFacC(i,j,bi,bj)
       + MAX( dPhiRef, 0. _d 0 ) *( rStarFacC(i,j,bi,bj) - 1. _d 0 )
       + phi0surf(i,j,bi,bj)

Thank you for your time,
Many thanks,

CJ
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