影响华北重度和轻度高温热浪的大气背景场差异分析  

Discrepancy in atmospheric background influencing severe and mild heat wave events over North China

作　　者：靳鑫桐 周波涛[1] 谢文欣 胡跃鹏 范怡 JIN Xintong;ZHOU Botao;XIE Wenxin;HU Yuepeng;FAN Yi(Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Key Laboratory of Meteorological Disaster,Ministry of Education/Joint International Research Laboratory of Climate and Environment Change,Nanjing University of Information Science&Technology,Nanjing 210044,China)

机构地区：[1]南京信息工程大学气象灾害预报预警与评估协同创新中心/气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室,江苏南京210044

出　　处：《大气科学学报》2024年第1期124-135,共12页Transactions of Atmospheric Sciences

基　　金：国家自然科学基金资助项目(41991285)。

摘　　要：首先识别了1961—2020年华北地区的高温热浪事件,在此基础上筛选出重度和轻度高温热浪事件多发年份,对比分析了重度和轻度高温热浪事件的时空变化特征以及大气背景差异。结果表明,重度和轻度高温热浪发生频次的高值区分别位于华北北部和中南部。自20世纪60年代以来,华北重度和轻度高温热浪事件频次均呈现显著的增长趋势,其中重度高温热浪事件频次的增加更为明显。对应华北重度高温热浪事件多发,东亚中纬度地区为准相当正压结构的异常反气旋性环流控制,华北地区位于异常反气旋性环流的东南部。在该异常环流背景下,华北地区上空呈现异常下沉运动、云量偏少、大气整体偏干。在异常下沉绝热增温的同时,晴朗干燥的配置有利于更多的太阳辐射到达地表,相应的向上长波辐射和感热通量增加,进一步加热近地表大气。在华北轻度高温热浪事件高发年,华北位于异常反气旋(东南侧)和气旋(西北侧)性环流之间,主要受异常西南风控制。异常西南风向华北输送暖平流加热大气的同时,增加了华北上空的水汽。偏多的水汽捕获更多的长波辐射并反射至地表,利于气温升高。A heat wave defined as several consecutive days with positive temperature anomalies.Since the 1950s,heat waves have increased in number and intensified globally,exerting significant impacts on human health,theecosystem,and the social economy.The increase in heat waves,especially extreme events with longer duration and higher amplitude over North China after the late 1990s,is of particular note.However,relevant existing studies have mainly focused on unsorted events or typical cases,and the atmospheric backgrounds of heat waves with different severities are unclear.Therefore,using the CN05.1 daily maximum temperature and NCEP/NCAR reanalysis data for the period of 1961—2020,this study identifies severe and mild heat wave events over North China,then selects the years with high frequencies of such events.On this basis,the spatiotemporal variation and atmospheric background of severe and mild heat waves events over North China are investigated through composite analysis.The results show that high frequencies of severe and mild heat wave events mainly appear in the northern part and the middle and southern parts of North China,respectively.For both types of events,their frequencies averaged over North China have shown a significant increasing trend since the 1960s,with a higher occurrence rate of severe heat waves(0.09 events per decade)than mild ones(0.03 events per decade).Corresponding to high frequencies of severe heat waves in North China,an anomalous anticyclonic circulation with the quasi-equivalent barotropic structure dominates the mid-latitudes of East Asia,and the North China domain is located in its southeast flank.Against this background,anomalous subsidence and hence reduction of cloud cover and humidity appear in North China.In addition to the adiabatic heating of the subsidence,the clear-dry air over North China is conducive to stronger solar radiation reaching the land surface.Accordingly,the outgoing longwave radiation and sensible heat from the land surface are enhanced,thus warming the overlying

关 键 词：重度高温热浪 轻度高温热浪 华北 大气背景 动力水汽条件 热力条件 

分 类 号：P433[天文地球—大气科学及气象学]