2005年夏季的主要天气及其环流分析

简要讨论了2005年夏季的主要天气过程和形势。2005年夏季全国大部分地区降雨量接近常年同期或偏多,特别是新疆地区降雨异常偏多,华南地区出现严重洪涝,而长江流域出现了空梅。造成6月华南地区强降雨的影响天气系统为切变线和地面静止锋,主要为从东北和西北来的冷空气与暖湿气流交汇于华南地区而形成。2005年与1994、1998年环流的对比表明,1998年西南季风强度比1994、2005年都要弱,但2005年梅雨期东阻位置在贝加尔湖东侧,比1998年的鄂霍次克阻高偏西,中纬度地区多小槽活动,贝加尔湖地区没有长波槽建立,中高层西风急流带偏北大约10个纬度,低层西南风急流也偏北,有利于北方降水的发生。2005年夏季登陆我国的台风偏多,强度较强,这是又一特点。华北地区的暴雨过程多与登陆或西太平洋上活动的台风有关;东北地区多低涡活动。与2004年对比,2005年华北地区的高温日数偏多,而且出现持续闷热天气,江南部分地区的高温天数也偏多。

The Weather and Its Circulation in Summer of 2005

The main weather processes and the related circulations are discussed.The total precipitation amount over most of China is almost equal to or more than climatologic one.The flooding occurred over Xinjiang Autonomous region and South China,but typical Meiyu over the Yangtze River valley did not occurred.The severe heavy rainfall over South China was caused by the shear line at lower troposphere and stationary front at surface,which was associated with the convergence of cold air from northwestern and northeastern China and warm-wet air from South China Sea.The comparison of summer monsoon circulation between 2005,1994 and 1998 shows that the summer monsoon in 1994 and 2005 was stronger than that in 1998.In the Meiyu season of 2005,the blocking high located to the east of Lake Baikal,small trough in westerlies was relatively active in middle latitude area.Comparing with the circulation in 1998,the westerly jet at upper troposphere and southwesterly jet at lower troposphere moved north farther about 10 latitudes.The landing tropical cyclones with high intensity were more than the normal and resulted in serious disasters.The heavy rainfall in North China was related to the activities of tropical cyclones over mainland or western Pacific Ocean.The vortices were very active over northeast China in the summer of 2005.The hot weather days over southern China and North China in the summer of 2005 are relatively more than that in the summer of 2004,and swelter weather also occurred over North China.In addition,hot weather days did not happen over northeast China.The hot wave occurred in southern and North China,which was associated with subtropical high of West Pacific and continental high,respectively.