Influence of the pace of El Nino decay on tropical cyclone frequency over the western north pacific during decaying El Nino summers  

作　　者：Qun Zhou Lixin Wei 

机构地区：[1]National Marine Environmental Forecasting Center,Ministry of Natural Resources,Beijing,China

出　　处：《Atmospheric and Oceanic Science Letters》2023年第3期39-45,共7页大气和海洋科学快报（英文版）

基　　金：supported by the National Natural Science Foundation of China[Grant No.41505050];the Open Fund of the Key Laboratory of Ocean Circulation and Waves of the Chinese Academy of Sciences[Grant No.KLOCW1902].

摘　　要：本文分析了El Nino事件衰减速度的差异对衰退年夏季西北太平洋热带气旋(tropical cyclone,TC)频数的不同影响。按照ElNiio事件衰减速度不同,将其划分为迅速衰减(rapid decaying,RD)和缓慢衰减(slowdecaying,SD)的El Nino事件.SD(RD)El Nino事件的衰退年夏季,赤道中东太平洋海温仍维持正异常(衰减为负异常).与SD El Nino事件相比,RDElNino事件衰退年夏季西北太平洋TC频数显著减少.进一步的分析揭示了导致TC频数差异的大尺度环境要素,指出热带印度洋-太平洋海温异常密切相关的西北太平洋低层反气旋异常在其中起到了关键作用。This study investigated the distinct responses of western North Pacific(WNP)tropical cyclone(TC)activity during different decaying El Nino summers.The El Nino events were classified into two types according to the periodicity of the ENso cycle,with positive SST anomalies in the equatorial central-eastern Pacific maintaining positive values into the following summer as the slow decaying(SD)cases,but transforming to negative values in the following summer as the rapid decaying(RD)cases.Compared with that in SD El Nino summers,the TC occurrence frequency over the WNP is significantly lower in RD El Nino summers,led by a much weaker WNP monsoon trough with more unfavorable environmental factors for TC genesis and development.Further examination showed that the apparent warming over the tropical Indian Ocean basin and cooling over the equatorial central-eastern Pacific contribute together to an enhanced lower-tropospheric anticyclone through modulation of the descending branch of the large-scale Walker circulation over the WNP,which may play a crucial role in suppressing the TC activity during the decaying summer of RD El Nino cases.In contrast,the warming equatorial central-eastern Pacific and remote western Indian Ocean induce a weakening WNP anticyclone and less suppressed deep convection during the decaying summer of SD El Nino cases.Thus,the different evolution of sST anomalies associated with different paces of El Nino decay results in the linkage between the preceding winter El Nino and the decreased WNP TC frequency in summer being more(less)robust for RD(SD)El Nino cases.

关 键 词：ElNino衰减速度 热带气旋 西北太平洋 低层反气旋 

分 类 号：P732[天文地球—海洋科学] P444