蒙古冷涡影响下的北京降雹天气特征分析  

Analyses on Weather Characters of Hail Event in Beijing with Mongolia Cold Vortex

作　　者：王在文[1] 郑永光[2] 刘还珠[2] 沃伟峰[2] 黄卓[3] 

机构地区：[1]北京城市气象研究所,北京100089 [2]中国气象局国家气象中心,北京100081 [3]中国气象局,北京100081

出　　处：《高原气象》2010年第3期763-777,共15页Plateau Meteorology

基　　金：国家科技支撑计划课题(2008BAC37B05);"北京奥运会国际天气预报示范计划关键技术研究"(2003BA904B08);国家自然科学基金项目(40875019)共同资助

摘　　要：蒙古冷涡是诱生北京地区冰雹天气的一种主要天气系统,通过对近8年几例冰雹天气过程的分析,得出在蒙古冷涡影响下,北京地区产生的冰雹天气与其他天气类型相比,具有分布范围广、局域性强的特点。对蒙古冷涡影响下的天气形势进行详细分析,可以进一步将其分为两类,一类是蒙古冷涡后部强冷空气与前部暖湿气流交绥,地面强冷锋造成的对流天气;另一类是主冷锋后,蒙古冷涡后部不断南下的冷空气,与增温、增湿的地面低涡或切变线系统而形成不稳定大气层结造成的对流天气。同时该两类天气也有许多共同特征。如对流层低层的能量锋,大气的斜压性和层结的条件对称不稳定激发了能量锋前蕴酿已久的湿有效能量得到了有效的释放,导致对流不稳定天气的发展。对流层中层干冷空气的侵入,正的差动假相当位温平流加剧了大气层结的不稳定,强的风垂直切变更促使对流上升运动的发展。尽管这两类冰雹的各项特征的强弱程度不同,所产生的冰雹天气强弱也有差别,但都表现了有利于冰雹天气发生和发展的动力、热力特点。与其它个例比较,可以综合提出蒙古冷涡影响下冰雹天气的预报着眼点,为北京地区强对流天气潜势预报和临近预报提供理论依据。Mongolian cold vortex is one of the main synoptic systems that may bring hail in Beijing area.In this paper,the several hail cases which occurred in Beijing during the recent 8 years are investigated. The result shows that under the influence of the Mongolian cold vortex,the hailstone can occur over a wider area and move localized in Beijing.The corresponding synoptic situation can be classified into two kinds： Firstly,the convection is caused by the strong cold front at surface,which is generated by the interaction of the strong cold air in the rear of the Mongolian cold vortex with the warm air ahead;secondly,the convection occurs after the cold front passing when the cold air in the rear of the Mongolian cold vortex interacts with the warm and wet surface low vortex or shear systems,convective unstable stratification is formed,and severe convection is produced.At the same time,there are many common characteristics for the two kinds,such as the existence of an energy front in the lower troposphere,the atmospheric baroclinicity and conditional symmetric instability of stratification.Once the moist available potential energy before the energy front is released,the unstable convective severe weather then occurs.The unstable stratification is intensified by the dry cold air intrusion in the middle troposphere and the advection of positive differential pseudo-equivalent potential temperature.The strong vertical shear of wind also enhanced the development of convective ascending motion further.Despite the intensity difference between the two hail categories,processes of similar dynamic and thermal characteristics which are in favor of the occurrence and development of hail events.These characteristics can be summarized to key points for forecasting the hail events under the influence of the Mongolian cold vortex,so as to provide the theory basis for the potential-and nowcasting-forecast of severe convective weather in Beijing area.

关 键 词：蒙古冷涡 冰雹 能量锋 条件对称不稳定 干冷空气侵入 

分 类 号：P458.121.2[天文地球—大气科学及气象学]