El Nino/Southern Oscillation Dynamics and Decadal Variability

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Clark 9617304 Two aspects of El Nino/ Southern Oscillation (ENSO), dynamics will be studied using historical data and simple dynamical models. The first problem deals the ENSO interaction between the western and central tropical Pacific where evidence suggests that low-frequency sea surface temperature in the western equatorial Pacific is associated with evaporation by anomalous winds. In addition, the suppressed convection in the western equatorial Pacific during a warm ENSO event results in winds being anomalously easterly there. These Easterlies will generate an equatorial upwelling Kelvin wave with a westward current that, by zonal advection in the central equatorial Pacific and upwelling in the eastern equatorial Pacific, can slow and perhaps reverse the original warm event as a negative feedback. The influence of this negative feedback will be tested with a coupled ocean atmosphere model. The second problem will look at the possibility that the decadal variability observed in the tropical Pacific records is an intrinsic part of the ENSO mechanism using simple and an intermediate coupled models.