中国大范围持续性极端低温事件年代际变化及其大气环流成因  

Interdecadal Variability of Extensive and Persistent Extreme Cold Events in China and Their Atmospheric Circulation Causes

作　　者：刘子奇 路瑶[1] 李艳[1] LIU Ziqi;LU Yao;LI Yan(School of Atmospheric Sciences,Lanzhou University,Lanzhou 730000,Gansu,China)

机构地区：[1]兰州大学大气科学学院,甘肃兰州730000

出　　处：《高原气象》2022年第3期558-571,共14页Plateau Meteorology

基　　金：国家自然科学基金项目(41775051)。

摘　　要：利用1961-2018年中国逐日温度观测资料和NCEP再分析资料,分析了我国大范围持续性极端低温事件(EPECE)年代际特征及大气环流成因。结果表明,EPECE累计天数在1961-2018年间总体存在波动下降的趋势特征,但在1995年前后出现了趋势转折,在1995年前事件累计天数减少趋势显著,且以全国类事件为主;1995年后变为增多趋势,主要类型为西北/江南类与中东部类事件。通过对大气环流场分析及利用西伯利亚高压指数、阻塞高压指数以及等熵面上的位涡(PV)异常特征分析,对比研究了1995年后西北/江南类与中东部类事件显著增多的大气环流成因,进一步发现,1995年EPECE事件期间欧亚大陆极涡由强转弱,乌拉尔山阻塞高压频率偏低至21.8%,西伯利亚高压强度指数距平最大值为8.9 hPa,位于乌拉尔山地区的异常低PV环流偏强,轴线呈东北-西南向,为典型的反气旋式Rossby波破碎,使得冷空气南下影响我国大部分地区。而在1996-2018年间EPECE事件发生时,欧亚大陆极涡在减弱过程中不断得到补充而维持,乌山阻高频率达34.6%且范围偏东偏北,西伯利亚高压强度距平达到11.5 hPa,位于贝加尔湖地区的高位涡相对偏弱,异常低PV环流能够从乌山向东向北移至贝湖以北,从而影响乌山阻高延伸至欧亚大陆中部,使得1996-2018年冷空气影响我国时能到达更南的地区,并能长时间维持。The interdecadal characteristics and atmospheric circulation causes of the extensive and persistent extreme cold events(EPECE)in China are analyzed in this paper based on NCEP/NCAR and the dataset CN05.1 of daily mean temperature from 1961 to 2018.The results show that there is an overall fluctuating decreasing trend characteristic of the occurrence days of EPECE from 1961 to 2018,but the trend turns around 1995,and the occurrence days of the events before 1995 have a significant decreasing trend,and the events are mainly of the countrywide type;after 1995,the trend becomes increasing,and the main types are the northwestern/Jiangnan type and mid-eastern type.By analyzing the atmospheric circulation field with the Siberia high index,blocking high index,and potential vorticity(PV)anomaly characteristics,the atmospheric circulation causes of the northwestern/Jiangnan type and mid-eastern type of events after 1995 were comparatively studied.The results further showed that the strong Eurasian polar vortex became weak during the EPECEs from 1961 to 1995,the frequency of blocking high in Ural was low at 21.8%,the maximum anomalies of the Siberia high index was 8.9 hPa,and the anomalous low PV circulation in Ural was strong with a northeast-southwest axis,which was a typical anticyclonic Rossby wave breaking,it allowed cold air to move southward to affect most parts of the country.During the EPECEs from 1996 to 2018,the Eurasian polar vortex was continuously replenished and maintained in the process of weakening,the frequency of Ural blocking high reached 34.6%and the range was east-north,the anomalies of Siberia high reached 11.5 hPa,and the high vortex air located in the Baikal region was relatively weak,and the anomalously low PV circulation was able to move eastward and northward from Ural to north of Lake Baikal,thus affecting the Ural blocking high can be extended to central Eurasia,making it possible for cold air to reach more southern regions and maintain it for a long time when it affected China during 1996-2018

关 键 词：大范围持续性极端低温事件 阻塞高压 西伯利亚高压 Rossby波破碎 

分 类 号：P461[天文地球—大气科学及气象学]