ENSO時の熱帯海面水温偏差と日本の冬の天候

Abstract

In the Far East, El Niño (La Niña) typically brings warm (cold) winter. However, significantENSO events have the opposite tendencies. To understand the cause of the disparate mid-latituderesponses, composite analysis has been conducted using long-term reanalysis dataset to find the seasurface temperature (SST) in the Pacific Ocean and the atmospheric responses corresponding to warm orcold winter in the Far East. Our analysis shows that about 70% of all ENSO are classified as the typicalwarm and about 30% as the atypical events. A Western Pacific (WP)-like meridional dipole patternappears in the typical events. Surprisingly, Pacific/North American (PNA) pattern, which is a remarkablefeature during ENSO, is obscure during the typical events. In fact, PNA pattern dominates during atypicalevents, with large amplitude. In addition, SST distributions differ in the west Pacific Ocean. During thetypical events, the amplitude of SST anomaly in the Philippine sea is large. In contrast to it, the anomalyis not clear in the atypical events. This SST anomaly in the west Pacific Ocean may cause atmosphericresponses in the mid-latitude consistent with the winter climate in the Far East during ENSO.