Interannual variation of oceanic precipitation

Twelve and a half years (July 1987-December 1999) of monthly rainfall data derived from SSM/I are used to study interannual variation of oceanic precipitation. Empirical orthogonal function analyses show that the dominant mode of interannual variation is the El-Nino Southern Oscillation (ENSO) pattern, exhibiting a correlation of 0.73 with a Southern Oscillation Index (SOI). Wavelet analyses of the SOI show high power concentration in the 3.5-5 year band starting from the late sixties, but the power peak was disrupted during the period July 1991-June 1995. SSM/I can provide the long-term history as a baseline for the more accurate TRMM and future GPM missions.