一次飑线风暴的环境条件和雷达回波特征分析

利用常规气象观测和新一代天气雷达监测资料,对大兴安岭地区加格达奇市2006年8月一次飑线天气的环境条件和雷达回波特征等分析发现：此次过程的影响系统高空槽为前倾结构,飑线发生在地面冷锋前,大气具有较强的不稳定层结,有利于上升运动,水汽充足,低层较强的垂直风切变使对流云团和弓形等线状回波生成并较长时间地维持和发展。对流云团位置与上升运动区域较为一致,产生飑线的强对流云团出现在中低层垂直速度梯度较大并靠近上升运动中心一侧,并位于低层比湿和水汽通量散度梯度较大区域即干锋附近以及K指数能量锋上。飑线弓形回波出现在一个中尺度椭圆状对流云团中心内部发展最强处。当云团向东北偏东方向移过加格达奇雷达站时,雷达反射率因子先后呈现出弓形、＂人＂字形等线状回波特征,当线状回波南端＂人＂字形顶部较强回波和后侧入流急流前方＂V＂型槽口的尖峰移经加格达奇时,带来了雷雨大风天气。

Analysis of the Environmental Conditions and the CINRAD CC Echo Characteristics of a Squall Line

Using the data of conventional meteorological observations and CINRAD-CC in Jiagedaqi of Daxing＇anling region in August 2006,the environmental conditions and the Doppler radar echo char-acteristics of the squall line near Jiagedaqi in midsummer were analyzed. The influencing system of the process was the upper trough,which was a forward structure,the squall lines occurred before the ground cold reached,the atmosphere had a strong unstable stratification,ascending motion was beneficial,the moisture was sufficient,and the stronger low-level vertical wind shear made the convective clouds and lin-ear echoes generate,maintained and developed for a long time. The position of convective clouds was more consistent with ascending motion region,the strong convective clouds generating squall line ap-peared in the side which lower vertical velocity gradient was larger and near ascending motion center,and located near the dry front and in the K index energy front. The bow echo of squall line appeared in the strongest development department of oval mesoscale convective cloud center. When the clouds moved to the ENE over Jiagedaqi radar station,the radar reflectivity factor had showed linear echo characteristics such as bow,chevron shape and so on. When a strong echo at the top of the southern of the chevron shape linear echo and the ＂V＂type notch peak in front of rear inflow jets moved through Jiagedaqi,the thunderstorm occurred.