Oceanic Equatorial Waves and the 1991–93 El Niño

Abstract

Abstract Equatorial Kelvin and Rossby waves associated with the 1991–93 El Nino warm event were detected in temperature observations made by the Tropical Atmosphere-Ocean (TAO) buoy array. Intraseasonal Kelvin waves were a prominent part of equatorial thermocline depth variability and were well represented by a simple model consisting only of first- and second-mode baroclinic Kelvin waves. The second mode was essential to properly represent the observed amplitude. Thermocline depth variability at 5°N and 5°S was dominated by annual and interannual Rossby waves, which were found to have been largely wind forced in midbasin, with little if any signal associated with eastern boundary reflection. An evaluation of the Wyrtki buildup hypothesis and the delayed oscillator hypothesis in connection with the 1991–93 events showed that a long lag (about two years) occurred between the arrival of the downwelling signal in the west and the subsequent initiation of El Nino., this was considerably longer than suggested ...