Important role of the ENSO combination mode in the maintenance of the anomalous anticyclone over the western North Pacific in boreal summer  

作　　者：Wenjun ZHANG Zuoli YU Feng JIANG Xin GENG Renhe ZHANG 

机构地区：[1]CIC-FEMD/ILCEC,Key Laboratory of Meteorological Disaster of Ministry of Education(KLME)/School of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China [2]Zhangjiagang Meteorological Bureau,Suzhou 215600,China [3]Institute of Atmospheric and Oceanic Sciences,Fudan University,Shanghai 200433,China

出　　处：《Science China Earth Sciences》2022年第7期1379-1387,共9页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.42125501&42088101)。

摘　　要：This study demonstrates the main physical mechanism for the maintenance of the western North Pacific(WNP)anomalous anticyclone(WNPAC)during the El Niño decaying summer by analyzing the respective effects of the cold sea surface temperature(SST)anomalies in the WNP,the warm SST anomalies in the Indian Ocean(IO),and the El Niño and Southern Oscillation(ENSO)combination mode.We find that the WNPAC is usually accompanied by significant cold WNP SST anomalies in the El Niño mature winter and following spring,which almost disappear in the decaying summer and cannot explain the maintenance of the WNPAC in summer.The influence of the IO warm SST anomalies on the WNPAC exhibits conspicuous decadal differences.Before the 2000 s,the IO warm SST anomalies played a role in the WNPAC maintenance through the response of the baroclinic atmospheric Kelvin wave;however,this effect cannot be evidently detected after the 2000 s.This decadal difference may be related to changes in the decaying speed of ENSO events.In contrast to El Niño events before the 2000 s,El Niño events after the 2000 s decay more rapidly,and the associated tropical central-eastern Pacific SST features a La Ni?a-like condition in the El Niño decaying summer.Concomitantly,no significant warm SST anomalies appear over the tropical Indian Ocean,exerting a weak influence on the WNPAC.Relative to the cold WNP SSTanomalies and warm IO SST anomalies,the ENSO combination mode,originating from the nonlinear interaction between ENSO and the annual cycle,has a relatively stable relationship with the WNPAC during the El Niño decaying summer,which exhibits a crucial role in the maintenance of the WNPAC.Considering the persistence of the ENSO combination mode,the WNPAC and associated climate variability during the El Niño decaying summer can be skillfully predicted at least one season in advance based on the ENSO combination mode.

关 键 词：ENSO WNP anomalous anticyclone ENSO combination mode 

分 类 号：P444[天文地球—大气科学及气象学]