两类厄尔尼诺事件对次年山东夏季降水的影响研究

Impacts of Two Types of El Nino on Summer Rainfall in Shandong

厄尔尼诺(El Nino)事件可根据海温极大值中心分为东部型El Nino和中部型El Nino。本研究通过观测资料研究了1979-2020年两类El Nino事件对次年山东夏季(6-8月)季节平均和月平均降水异常的影响。结果显示,中部型El Nino次年夏季西北太平洋反气旋较气候态偏北,进而增强东亚夏季风,使得山东夏季平均降水偏多。伴随着反气旋在季节内的北移,降水正异常在晚夏(8月)最为显著,而东部型El Nino次年夏季反气旋较气候态偏南偏弱。同期日本列岛地区由于东亚-太平洋遥相关负位相的出现产生异常气旋,山东地区受气旋西侧干冷北风控制,夏季降水偏少。由于气旋强度在季节内逐渐降低,所以山东干旱在初夏(6月)最显著。这些结果可以为未来山东夏季降水季节预测提供重要参考。

The El Nino events can be classified into EP El Nino and CP El Nino according thelocation of the warmest SST anomaly(SSTA).Based on the composite analysis,this paper analyzes the differences of summer rainfall in Shandong Province and related possible mechanisms during the decaying stage of two types of El Nino events.The results can be concluded as follows:In the following summer of CP El Nino,the anomalous Northwest Pacific Anticyclone(NWPAC)shifts northward to increasing the summer rainfall in Shandong through intensifying the water vapor transport of East Asian summer monsoon.The precipitation is most significant in August,which is related to the intraseasonal northward movement of the NWPAC.In contrast,during the following summer of EP El Nino,NWPAC shifts southward,generating a negative East Asia-Pacific teleconnection pattern with a cyclonic anomaly over Japan.This strengthen the East Asian trough,leading to more droughts in Shandong,especially during June.These results can promote the skill of seasonal prediction on summer precipitation in Shandong.