晚春北极涛动对夏季西北太平洋热带气旋生成频数的影响  

Impacts of the late spring Arctic Oscillation on the summer tropical cyclone frequency over the western North Pacific

作　　者：周群[1] 魏立新[1] Zhou Qun;Wei Lixin(National Marine Environmental Forecasting Center,Beijing 100081,China)

机构地区：[1]国家海洋环境预报中心,北京100081

出　　处：《海洋学报》2021年第1期82-92,共11页

基　　金：国家自然科学基金青年基金项目(41505050);中国科学院海洋环流与波动重点实验室开放基金项目(KLOCW1902)。

摘　　要：利用美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)再分析资料以及中国气象局发布的热带气旋(TC)最佳路径数据集,本文探讨了1950–2018年期间晚春(5月)北极涛动(AO)与随后夏季(6–9月)西北太平洋上空热带气旋生成频数的关系。研究表明,晚春AO对夏季西北太平洋TC生成有明显的预报指示意义,二者之间存在显著的正相关关系。对应晚春AO指数偏高年,夏季西太平洋副热带高压主体位置偏东偏北、强度偏弱,西北太平洋上空大气低层有较强的辐合、高层辐散增强、中层水汽充足、垂直风切较弱,这些大尺度环境因子均有利于TC的生成。而在晚春AO指数偏低年,西北太平洋上空的大气环流特征与上述特征相反,造成TC生成频数偏少。进一步的分析揭示:与AO变化密切相关的北太平洋风暴轴位置的南北移动,在晚春AO与夏季西北太平洋TC生成频数二者关系中起到了关键作用。AO正位相(负位相)年,北太平洋风暴轴向北(向南)偏移,通过天气尺度波动和平均流之间的相互作用,造成后期夏季西北太平洋上空低层形成气旋性(反气旋性)涡度异常,在局地经向环流的调整作用下,西北太平洋副热带高压的位置及强度发生改变,对西北太平洋TC的形成起到了促进(抑制)作用。In the present study,the connection between the Arctic Oscillation(AO)in May and the following summer(June to September)western North Pacific tropical cyclone genesis frequency is investigated based on NCEP/NCAR reanalysis data and tropical cyclone data from China Meteorological Administration for the period 1950–2018.A statistically significant positive correlation is found between the late spring AO and summer tropical cyclone genesis frequency.The diagnosis results show that the low-level relative vorticity,high-level divergence,vertical wind shear and the mid-low level relative humidity are all beneficial for the genesis of the western North Pacific tropical cyclones during the positive AO years.Moreover,the western Pacific subtropical high shifts eastward and northward and tends to be much weaker.On the contrary,during the negative AO years,the tropical cyclone formation is reduced because of the strengthened western Pacific subtropical high combined with an anticyclonic vorticity in the lower troposphere.The possible mechanism involved the variations of the storm track in the North Pacific.It is showed that during the positive(negative)AO years the storm track is moving northward(southward)and there is a cyclonic(an anticyclonic)vorticity anomaly in the lower troposphere in the western North Pacific in the subsequent summer through the interaction between the synoptic-scale eddies and low-frequency mean flow.The resulting anomalous local Hadley circulation could lead to the change of the western Pacific subtropical high and further contribute to the western North Pacific tropical cyclogenesis.

关 键 词：北极涛动 热带气旋 西北太平洋 风暴轴 

分 类 号：P444[天文地球—大气科学及气象学]