Interdecadal Changes in the ENSO–Monsoon System

Abstract

The El Nin o-Southern Oscillation (ENSO) and Indian monsoon are shown to have undergone significant interdecadal changes in variance and coherency over the last 125 years. Wavelet analysis is applied to indexes of equatorial Pacific sea surface temperature (Nin o3 SST), the Southern Oscillation index, and all-India rainfall. Time series of 2-7-yr variance indicate intervals of high ENSO-monsoon variance (1875ENSO-monsoon variance ( -1920ENSO-monsoon variance ( and 1960-90) -90) and an interval of low variance . The ENSO-monsoon variance also contains a modulation of ENSOmonsoon amplitudes on a 12-20-yr timescale.