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

[秋菊陳]

Greetings,

I would like to get some clarification about the variable PHIHYD, both
physical meaning and to relate the value with other variables (SSHDYN,
RHOAnoma and EXFpress).
(e.g.
https://data.nas.nasa.gov/ecco/data.php?dir=/eccodata/llc_90/ECCOv4/Release4/interp_daily.
Yes, I am a ECCO data user.)

To my understanding, PHIHYD is the hydrostatic-pressure-anomaly/1029. The
other way round, we could consider "PHIHYD*1029" as the sum of
hydrostatic-pressure-anomaly ABOVE.
>From the schematic figure-1 below, the hydrostatic-pressure-anomaly of the
first grid PHIHYD(1)*1029 could be treated as sum of 3 components:
(1) atmospheric pressure (EXFpress),
(2) sea water pressure from sea surface (eta, SSHDYN) to z=0, i.e. g*(
RHOAnoma+1029 )*SSHDYN
(3) sea water pressure from z=0 to first data grid z(1), i.e.
g*RHOAnoma*abs(z(1))

However, I cannot get the result [sum of 3 components, fig2a green line]
close to PHIHYD(1) [fig2a black line], unless ignoring component (2) [fig2a
red line]. Did I misunderstand something?
Any help would be appreciated.

Best,

CJ





Figure-1
                                                              Figure-2
[image: schematic.png]             [image: check_PHIHYD1_nasnasa.png]
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