The 30–60-Day Convection Seesaw between the Tropical Indian and Western Pacific Oceans

Abstract

Abstract The tropical Indian and western Pacific oceans are two prominent action centers for tropical 30–60-day convective variability. When convection is enhanced over the equatorial Indian Ocean, the tropical western Pacific often experiences an abnormal dry condition (phase I), whereas the development of the convection over the tropical western Pacific tends to be accompanied by suppressed convection in the equatorial Indian Ocean (phase II). This convection seesaw is a fundamental characteristic of the tropical 30–60-day oscillation. The seesaw is intimately associated with the activity of propagating low-frequency convective systems (LFCSs). Its formation process is season dependent. Typical boreal summer seesaw results from a time-lagged development of two systems: a western system that originates in the equatorial Indian Ocean and moves eastward and/or northward and an eastern system that develops in the western Pacific monsoon region and moves westward and/or northward. The boreal winter seesaw, o...