Equatorial waves and the 1997-98 E1 Nifio

Abstract. New measurements and model results highlight the role of equatorial oceanic wave processes in affecting the evolution of the 1997-98 E1 Nifio in ways not fully antici-pated by delayed oscillator theory, a leading paradigm for the E1 Nifio/Southern Oscillation (ENSO) cycle. The onset of the E1 Nifio was linked to eastward propagating equa-torial Kelvin waves forced by intraseasonal atmospheric os-cillations originating over the Indian Ocean. The demise of the E1 Nifio was related to a complex interplay of wind-forced and western boundary-forced waves that precondi-tioned the ocean to sudden sea surface temperature cool-ing initially centered between 125øW and 170øW along the equator. These large-scale ocean wave processes, and the ocean-atn'losphere interactions that they mediate, have sig-nificant implications for understanding variability associated with E1 Nifio-related climate swings. 1