STUDY OF ANOMALOUS SST FIELD IN TROPICAL PACIFIC IN PRECEDING YEARS OF TWO PATTERNS OF ENSO EVENTS

Analyzing the anomalous field of SST over the tropical Pacific for two kinds of ENSO events after 1956. we find that in the preceding year before the eastern pattern of El Nino event there is the La Nina event and large negative anomalies of SST in the tropical central and eastern Pacific; the preceding year before the eastern pattern of La Nina event witnesses the prevalence of the El Nino event and large positive anomalies of SST in the same waters: the preceding year before the central patterns of the El Nino (La Nina) events are generally marked by significant positive (negative) SST anomalies in central/western (eastern) tropical Pacific. The fields are just the opposite for two patterns of ENSO events. For waters in the warm pool in the western tropical Pacific, the central (eastern) pattern of El Nino event is with a warm (cool) preceding year of the pool. The warmer conditions in the western Pacific warm pool are a necessity for the occurrence of the central pattern of El Nino event.