Kessler 1991 Abstract
Can reflected extra-equatorial Rossby waves drive ENSO?
Kessler, W.S., 1991
Journal of Physical Oceanography, 21, 444-452.
The possibility that the evolution of the ENSO phenomenon is determined by the reflection of extra-equatorial Rossby waves from the western boundary into the equatorial waveguide has been a subject of recent debate. Observations and some wind-driven models suggest an apparent continuity of off-equatorial signals
and subsequent waveguide anomalies. On the other hand, coupled model results
show that ENSO-like behavior can be simulated with no involvement of extra-equatorial regions. Linear equatorial wave theory shows that significant
reflection can only occur within about 8 ° of the equator, with a sharp
fall-off in the reflectivity poleward of this latitude. Although the amplitude
of the thermocline anomalies associated with the observed ENSO-forced extra-
equatorial Rossby waves can be large, it is the the net zonal transport of these
waves that is crucial to the reflectivity, and this net transport decreases
rapidly as Rossby waves occur farther from the equator. The zonal geostrophic
flows associated with observed extra-equatorial Rossby waves in the northern
tropical Pacific do not provide a net transport that could make a
significant contribution to equatorial Kelvin waves. If the extra-equatorial
signals do exert an influence on the equatorial waveguide, it must be
through a mechanism other than simple boundary reflection.
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