一次飑线过程雷达回波特征及环境条件分析

利用常规资料、NCEP/NCAR再分析资料及多普勒天气雷达资料等,对2014年3月30—31日广东一次飑线过程进行了分析。重点分析了飑线发生的环流背景、环境特征、不稳定条件、垂直风切变等及多普勒雷达回波演变过程。结果表明:(1)此次飑线过程发生在中高纬地区稳定的阻塞形势下,从四川盆地东移的高空槽和低涡切变线是造成广东强对流天气的主要影响系统。(2)低空急流水汽输送、低层强水汽辐合、强低空垂直风切变和上干下湿的水汽垂直分布为飑线的发生、发展提供了必要的热力和动力条件。(3)强盛阶段飑线具有明显的阵风锋和弱回波通道,速度图上飑线北端为强的气旋式切变,南端为弱的反气旋式切变,在"弓形"回波顶点处有强的速度辐合。飑线内部后侧为一支倾斜向下的冷空气入流,前沿是一支沿冷空气爬升的暖空气入流。(4)在"弓形"回波顶部后侧长时间维持着向后倾斜的后侧入流急流RIJ(Rear Inflow Jets),RIJ对"弓形"回波的形成、地面大风和飑线的维持和快速移动具有重要的作用。

Analysis on radar echo characteristics and environmental conditions of a squall line

The conventional observation data, NCEP/NCAR reanalysis data and Doppler radar data are used to analyze the squall line process happened in Guangdong during 30-31 March, 2014. The circulation background of environmental characteristics, unstable situation, vertical wind profile and Doppler radar echo evolution process are emphasized. Results show:(1)the squall line occurred in a stably maintained blocking situation of middle-high latitudes. The upper trough moving eastward from Sichuan basin and low vortex shear line are the main influencing systems causing strong convective weather of Guangdong.(2) Low-level jet vapor transportation, strong low-level moisture convergence and vertical wind shear, as well as dry upper and wet lower vapor vertical distribution provide necessary thermodynamic and dynamic conditions for the formation and development of the squall line.(3)There obviously exists gust front and weak echo channel at the strong stage of squall line. The strong cyclonic shear appears in the northern part of velocity map, and the weak anticyclonic shear is in the southern part. There is strong speed convergence in the vertex of bow echo. Sloping-downward cold air inflow is inside the back of squall line, and a warm air inflow climbing along the cold air is in the front.(4) Rear Inflow Jets(RIJ), sustaining for a long time in the top of bow echo back, plays an important role for the formation of bow echo and for the maintenance and fast moving of surface wind and squall line.