中国东北夏季极端高温的分类及其与北大西洋海表温度异常的联系
投稿时间:2020-03-22  修订日期:2020-04-05  点此下载全文
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作者单位E-mail
李经纬 南京信息工程大学 1164040101@qq.com 
曾刚 南京信息工程大学 zenggang@nuist.edu.cn 
杨效业 南京信息工程大学  
张顾炜 南京信息工程大学  
基金项目:国家重点研发计划专项(2017YFA0603800);国家自然科学基金项目 (41575085,41430528)
中文摘要:本文通过对1979-2016年中国东北夏季259次极端高温事件爆发当天的500 hPa高度场进行层次聚类分型,将中国东北地区的夏季极端高温事件进行了分类,并讨论了各类极端高温事件的环流演变及其与北大西洋海表温度异常的联系。结果表明,东北夏季极端高温事件可分为三类,即西风型、阻塞型和波列型极端高温事件,在1979-2016年期间它们分别发生了113次、89次和57次。西风型高温事件的主要环流特征为极涡偏强,浅脊在准平直西风引导下在西风带内东移,当反气旋异常控制中国东北地区上空时,形成高温天气;阻塞型极端高温事件的主要环流特征为乌拉尔山阻塞高压偏强,中国东北地区位于高压脊前,西北气流下沉加热,导致中国东北地区高温。波列型极端高温事件的环流主要特征为欧亚大陆上空为“ - ”波列型环流异常,中国东北地区受反气旋环流异常控制形成极端高温,由于上游波能量的维持,该类极端高温事件的持续时间、影响范围和强度均强于前两类。通过对这三类极端高温事件发生前10-20天海表温度异常的合成分析,发现西风型和阻塞型这两类极端高温事件发生前,北大西洋无显著海表温度异常,而波列型极端高温事件发生前,北大西洋热带海域海表温度有显著的正异常,该海域海表温度异常与波列型极端高温事件强度变化呈显著正相关。回归分析的结果表明,北大西洋海温正异常有利于夏季欧亚大陆上空纬向波列型环流异常的维持,对波列型高温事件的发生提供了有利条件。
中文关键词:极端高温  中国东北  分类  海温异常  北大西洋
 
Classification of Summer Extreme High Temperature events in Northeast China and Its Relationship with Surface Temperature Anomaly in North Atlantic
Abstract:From 1979 to 2016, Northeast China experienced 259 summer extreme high-temperature (EHT) events. This study uses the Hierarchical Clustering method to classify the 500hPa height anomalies of those EHT events and investigates their circulation evolutions and their relationships with sea surface temperature (SST) anomalies in the North Atlantic. Results show that summer EHT events in Northeast China can be divided into three types namely the westerly-type, blocking-type and wave-train type with the occurrences of 113, 89 and 57 during 1979-2016 respectively. The main feature of atmospheric circulation in westerly-type EHT is that there is a stronger polar vortex than normal and a shallow ridge moves eastward along the Westerlies. With the guide by westerly, it then forms an anticyclone anomaly over Northeast China, thereby resulting in an EHT event over there. When a blocking-type occurs, its corresponding atmospheric circulation shows that a blocking high over the Ural gets stronger, and the northwest airflow sinks and heats Northeast china where locates in the front of the high ridge, thus leading to the extreme high-temperature event. The last type is wave-train type, which has a feature of the " - " wave-train circulation anomaly over Eurasia in the troposphere, and Northeast China is controlled by an anticyclone anomaly and thus forms a high-temperature event. Due to the maintenance of upstream wave energy, the duration, range of influence and intensity of wave-train-type events are stronger than those of the other two types. Based on the composites of SST anomalies 10-20 days before the occurrence of these three types of EHT events, it is found that there are no significant SST anomalies in the North Atlantic before the occurrence of westerly-type and blocking-type events. A significantly positive anomaly in the tropical North Atlantic is observed when a wave-train-type event happens. The SST change in the North Atlantic is positively correlated with the intensity of the EHT event. The regression analysis result illustrates that the North Atlantic SST positive anomaly is conducive to the maintenance of zonal wave train circulation anomaly over Eurasia in summer, and provides favorable conditions for the occurrence of wave-train type EHT events.
keywords:Extreme high temperature  Northeast China  Classification  Sea surface temperature
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