FY 2000

Equatorial waves and the 1997–98 El Niño

McPhaden, M.J., and X. Yu

Geophys. Res. Lett., 26(19), 2961–2964, doi: 10.1029/1999GL004901 (1999)

New measurements and model results highlight the role of equatorial oceanic wave processes in affecting the evolution of the 1997-98 El Niño in ways not fully anticipated by delayed oscillator theory, a leading paradigm for the El Niño/Southern Oscillation (ENSO) cycle. The onset of the El Niño was linked to eastward propagating equatorial Kelvin waves forced by intraseasonal atmospheric oscillations originating over the Indian Ocean. The demise of the El Niño was related to a complex interplay of wind-forced and western boundary-forced waves that preconditioned the ocean to sudden sea surface temperature cooling initially centered between 125°W and 170°W along the equator. These large-scale ocean wave processes, and the ocean-atmosphere interactions that they mediate, have significant implications for understanding variability associated with El Niño-related climate swings.