The close relationship of the El Nio occurrence with the positive anomalies of the sub-surface ocean temperature (SOT) in the Pacific warm pool region is studied through the data analyses. It is shown that there are continued positive anomalies of SOT in the warm pool region prior to the occurrence of El Nio event; The outbreak of El Nio event is directly associated to the eastward propagation of positive anomalies of SOT in the warm pool region and expanding to the sea surface in the equaorial eastern Paci...