310 Martin Fischer
ENSOCycle
+
intennediate phase
..- - ....
/
,
I
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\
I
..l
1
I
\
I
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,
/
.... - -
/
t
-
/
- ....
/
,
I
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I
\
EI Nino
\
I
'\
I
/
,
/
.... , -
t
/
- ....
/
,
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\
.1.
I
intermediate phase
\
I
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I
,
/
....
-
/
t
/
- ....
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"I
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I
La Nina
I
I
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,
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....
-
/
Fig. 16.2 Schematic description of heat content anomalies, following the theory of thr
delayed action oscillator. Due to easterly wind anomalies an eastward propagating Kelvin
wave packet and westward propagating Rossby waves are generated. The Rossby waves are
reflected at the westem boundary and cause a westward propagating equatorial Kelvin wave
packet ofthe opposite sign. The wind arrows represent the dominant wind anomalies.
by about one to three degrees centigrade in the equatorial east Pacific. It is important to note that this phenomenon occurs due to unstable air-sea interactions. It is a
feature of the coupled ocean-atmosphere system in the tropical Pacific. However,
the inertia of the ocean govems the evolution and time scale of ENSO. The impor-