El Niño and Tropical Pacific Ocean Surface Temperatures

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Abstract The spatial and temporal character of El Nino is explored with analyses of tropical Pacific Ocean surface temperatures for the period 1957–76. The data are derived from approximately 5×106 marine weather reports. Maps are illustrated which portray the initiation, maturation and decay of an “average” El Nino event. Empirical orthogonal functions of nonseasonal departures are displayed. The time coefficients of the dominant empirical functions are derived together with average departures for 18 regions which are usually 10° of latitude and 40–50° of longitude in size. Lag correlation and coherence-spectral analysts are carried out on all of the time series. The pattern of El Nino which is portrayed is that of a basinwide phenomenon with a time evolution lasting more than 24 months. During this evolution sea temperatures in the western Pacific tend to have departures of opposite sign to those in the cast. Variations in the eastern equatorial region are shown to precede those in the central equatoria...