冬季極東域における寒暖で分類したEl Niño発生時の中高緯度大気の応答

Abstract

It is well-known that El Niño typically brings warm winter in the Far East and that Western Pacific (WP) and Pacific/North American (PNA) often appear. However, significant events have opposite tendencies. To understand the cause of the difference, composite analysis has been conducted using long-term reanalysis datasets. Our analysis shows that about 63% of El Niño events occurred from1948 are classified as the warm and about 37% as the cold events. Furthermore, the WP and PNA seem to be mutually exclusive and are dominant during warm and cold winters, respectively. The SST anomaly in the Philippine Sea is negative more than that during cold winter. The SST anomaly distribution is corresponding to the Walker circulation anomaly. These differences are appeared from the fall and developed to the winter. Therefore, it is suggested that the disparate mid-latitude responses are associated with SST and the Walker circulation variations in the western Pacific Ocean.