Monthly Oceanic Rainfall from SSM/I for Climate Studies

Long Chiu
Center for Earth Observing and Space Research
George Mason University
Fairfax VA 22030
lchiu@gmu.edu

About seventeen years of monthly oceanic rainfall data produced from Special Sensor Microwave Imager (SSM/I) data taken on board the DMSP satellites using the technique developed by Wilheit, Chang and Chiu (WCC) are used to examine the diurnal and interannual variability of oceanic rainfall. Diurnal ocean rainfall is examined by combining the morning and afternoon satellite passes. The global oceanic diurnal cycle shows a early morning maximum whose amplitude and phase are comparable to that estimated from Tropical Rainfall Measuring Mission (TRMM) data. An Empirical Orthogonal Function analysis was performed on the non-seasonal data set. The first EOF pattern shows an east-west and north –south seesaw in the tropical Pacific, which can be interpreted as an El Nino Southern Oscillation (ENSO) pattern. The time series also shows a high correlation with an index of the Southern Oscillation. An Empirical Mode Decomposition of the time series shows distinct ENSO events against a relative stable background, suggesting the robustness of the WCC technique for rainfall estimation.

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