Geoscience Reference
In-Depth Information
Fig. 7
Pressure time series
in November 2011 at station
PPTE in Presidente Prudente,
Brazil
966
964
962
960
958
956
954
16
17
18
19
20
21
22
23
24
they are labelled in the same way, e.g.
S
1
and
S
2
(Brzezinski et al.
2002
). Exemplar-
ily, Fig.
7
shows the pressure measured at Presidente Prudente in November 2011,
and the
S
1
and
S
2
pressure variations are clearly visible.
2.8 Inverted Barometer Hypothesis
For this section, we mainly follow Schuh et al. (
2003
). The oceanic response to
atmospheric pressure variations is often considered to be static, causing an immediate
and compensating local deformation of the sea surface. This vertical change in sea
level
ζ
IB
is related to the atmospheric pressure variation
δ
p
a
with
ζ
IB
=−
δ
p
a
ρ
0
·
(39)
g
applying a hydrostatic approximation (Gill
1982
). As can be seen in Eq.
39
a positive
pressure anomaly is accompanied by a decrease of sea surface height; thus there is
an
inverted barometric
(IB) effect. For example, 1hPa corresponds to 1 cm.
Considering time spans long enough compared to the response time of the ocean
due to inertia, the IB hypothesis assumes a complete compensation of horizontal
gradients of pressure by ocean height
without impacting the dynamics of the ocean
or the ocean bottompressure. At every depth
h
the pressure stays constant considering
the atmospheric pressure change
ζ
δ
p
a
:
h
ζ
+
ζ
IB
ρ
·
h
−
ρ
·
g
·
dz
=−
g
·
dz
+
δ
p
a
(40)
ζ
Assuming IB behavior with its static approximation, all processes like currents
caused by the isostatic compensation are neglected. The effects can be triggered
