Oceanic equatorial waves and the 1991-93 El Nino

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. 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. This shows that the El Nino-Southern Oscillation cycle cannot be viewed simply as an oscillator mediated by the western boundary reflection of equatorial Rossby waves and that a buildup of a thick warm layer in the west is not a prerequisite to the occurrence of El Nino. -from Authors