Equatorial waves and the 1997-98 El Nino

New measurements and model results highlight the role of equatorial oceanic wave processes in affecting the evolution of the 1997-98 El Nino in ways n ot fully anticipated by delayed oscillator theory, a leading paradigm for t he El Nino/Southern Oscillation (ENSO) cycle. The onset of the El Nino was linked to eastward propagating equatorial Kelvin waves forced by intraseaso nal atmospheric oscillations originating over the Indian Ocean. The demise of the El Nino was related to a complex interplay of wind-forced and wester n boundary-forced waves that preconditioned the ocean to sudden sea surface temperature cooling initially centered between 125 degrees W and 170 degre es W along the equator. These large-scale ocean wave processes, and the oce an-atmosphere interactions that they mediate, have significant implications for understanding variability associated with El Nino-related climate swin gs.