内蒙古高温酷暑天气时空分布特征及成因分析

应用1971～2008年内蒙古自治区117个观测站资料,选取64次较强高温酷暑天气过程,结合同期的NCEP再分析资料,应用统计分析和诊断分析方法,对内蒙古高温酷暑天气的时空分布特征及成因进行了分析。结果表明:内蒙古高温酷暑天气地域差异大,高温中心在阿拉善盟沙漠地区的拐子湖,年平均35℃高温日数达32天,也是全国的高温区之一;高温酷暑年日数有增长趋势,影响在增强;高温酷暑集中出现在盛夏季节6～8月,7月发生最多,占一半以上;最高温度出现在每日的14至17时,气温日较差大;高温酷暑天气可分为蒙古暖脊型、贝加尔湖高压坝型、副高西进型、乌拉尔山高脊型四个天气学类型,大陆暖高压脊的强烈发展和维持与高温酷暑天气密切相关;300hPa高空锋区的北退或断裂与大陆暖高压系统的形成和发展有很好的相关性;对流层中层的暖平流对大陆暖高压系统的发展强盛起到关键作用;500～850hPa厚度场可以更好的反映出整层气柱冷暖性质,其分布特征直接影响到内蒙古高温酷暑天气发生的部位和区域;蒙古暖高压控制区中盛行下沉气流,使得大气下沉增温,对流层中低层维持暖心结构,由于整层气柱很暖,低层减压形成了近地层的热低压,具有干热的特征。

Temporal and spatial distribution of Inner Mongolia megathermal weather and cause analysis

By using observation data of 117 stations data in Inner Mongolia and NCEP reanalysis data from 1971 to 2008,64 strong megathermal processes were selected to analyze the temporal and spatial distribution and causes of Inner Mongolia megathermal weather using statistical analysis and diagnostic analysis method.The results showed that in Inner Mongolia summer megathermal weather shows great geographical differences;Guaizihu in the Alashan Desert is not only the high-temperature center in Inner Mongolia,but also one of high-temperature center in China.Where the days with annual average 35℃ is upto 32 days.The number of high-temperature days is increasing,also the influence is enhanced.The megathermal weather is concentrated in the summer from June to August,the most in July,which accounting for more than half of the megathermal weather.The daily maximum temperature appears at from 14 o’clock to 17 o’clock.The megathermal weather can be divided into four synoptic type which are Mongolia warm ridge,Lake Baikal high dam type,the westward extension of subtropical high type and Ural high mountain ridge type.The strong development and continuation of continental warm high ridge are closely related to megathermal weather.300hPa upper front northward retreating or fracture has good relevance with the formation and development of continental warm high pressure system.The warm advection in the middle troposphere plays a key role in the development of continental warm high pressure system.The distribution of 500~850hPa thickness field which can better reflect the whole layer air column properties directly affects the Inner Mongolia megathermal weather region.Area of Mongolia warm high pressure is prevalent downdraft which making the atmosphere sinking warming and thus maintaining the warm core structure in the troposphere.Because the whole layer column is warm,the decompression in the inferior atmospheric layer leads to form the surface thermal low which is dry and heat.