中国冬季两类极端低温事件特征及其大气环流成因分析  

Analysis of the Characteristics and Atmospheric Circulation Causes of Two Types of Extreme Cold Events in Winter in China

作　　者：刘明歆 李艳[1] 吕春艳 LIU Mingxin;LI Yan;LÜChunyan(Key Laboratory of Arid Climate Change and Disaster Reduction of Gansu Province/College of Atmosphere Science,Lanzhou University,Lanzhou 730000,Gansu,China)

机构地区：[1]兰州大学大气科学学院/甘肃省干旱气候变化与减灾重点实验室,甘肃兰州730000

出　　处：《高原气象》2021年第3期603-620,共18页Plateau Meteorology

基　　金：国家自然科学基金项目(41775051);甘肃省自然科学基金项目(18JR3RA301)。

摘　　要：近年来,中国冬季极端低温事件逐渐增多,其天气表征和成因存在很大差异。本文将极端低温事件分成大范围持续性低温事件(EPECE)和普通寒潮事件(CWE)两类,对其特征和大气环流成因进行了分析。结果表明:CWE平均维持3~5天,过程期间降温迅速并很快升温、降水出现在过程前期;而EPECE平均维持超过15天,降温幅度更大、降温范围更广、降水主要在过程后期。进一步分析环流成因发现,在EPECE中,事件开始前11(-11)天时对流层波动出现异常信号并上传,平流层极涡中心偏东,-9天时出现异常向东扩展的反气旋式Rossby波破碎(AWB)又将能量下传至对流层,阻塞高压异常向东扩展至90°E,阻塞强度最大超过24,阻塞频率最大超出气候态50%,西伯利亚高压的强度增强到1053 hPa。上述异常维持至过程发生后7(+7)天,从而使得冷空气爆发时降温剧烈、持续时间长。而CWE中前兆信号出现相对较晚,-3天时平流层极涡中心位于极点附近,伴随第0天出现AWB,乌拉尔山地区阻高异常局限在60°E附近,阻塞强度最大超过20,阻塞频率最大超出气候态45%,西伯利亚高压强度达到1050 hPa。+3天后,各环流系统的异常几乎消失,因而降温虽然剧烈但维持时间较短。There has been an increase of extreme cold events in China for the past few years,with distinctly different characteristics and causes of formation. The extreme cold events are classified into two types,i. e. the extensive and persistent extreme cold events(EPECE)and the cold wave events(CWE). The results show that the average duration of CWE is 3~5 days. During the process,while the temperature drops rapidly,it also rises quickly. The precipitation occurs in the early stage of the process. In contrast,EPECE lasts for more than 15 days on average,with a more drastical temperature drop and a wider temperature reduction range. The precipitation mainly occurs in the later stages of the process. With further analysis of the cause of atmospheric circulation,the anomalies of tropospheric system appear at 11 days prior to(-11)the event,indicating wave anomalies are transmited to the stratosphere in the EPECE. It makes the center of stratospheric polar vortex to be further east. The energy is transmitted down to the troposphere with the anticyclonic Rossby wave breaking(AWB)which extends eastward at-9 days. The blocking high abnormally extends eastward to 90°E. The maximum blocking intensity exceeds 24,and the maximum blocking frequency exceeds 50% of the climatology. The intensity of Siberian high pressure increases to 1053 hPa. The above abnormalities maintain until 7(+7)days after the occurrence of the event. As a result,when the cold air breaks out,the temperature is drastically reduced with a longer duration.By comparison,there are no such premature precursor signals in CWE. Accompanied by AWB at day 0,the center of the stratospheric polar vortex is near the pole at-3 days. The maximum blocking intensity exceeds 20,and the maximum blocking frequency exceeds 45% of the climatology. But the blocking limited to 60°E around Ural Mountain area. The maximum intensity of the Siberian high reaches 1050 hPa. +3 days later,the anomalies of the circulation systems almost disappeared. Therefore,in the CWE,the temperature drop

关 键 词：极端低温事件 极涡 阻塞高压 西伯利亚高压 Rossby波破碎 

分 类 号：P466[天文地球—大气科学及气象学]