一次强飑线及飑前中小尺度系统特征分析

Characteristics of Mesoscale and Microscale Systems During a Severe Squall Line Process

使用常规天气、灾情、自动站、卫星云图、雷达回波和风廓线雷达等资料,采用统计对比分析和特征提取等方法,对2012年4月10日强飑线天气系统进行分析和研究,结果表明:(1)此次强飑线是由若干个倾斜深厚对流单体所组成,具有紧密排列的回波带结构。(2)云图上表现为中尺度对流系统(MCS)结构特征,随着MCS东移降水冷却、西南气流输送暖湿空气和午后地面温度不断升高,地面开始形成温度梯度较大的温度锋区。(3)飑线形成前期,MCS南侧出现多条平行短带"梳状"回波特征,并在其南端不断产生对流单体回波,最后发展成飑线回波带。(4)飑线移动前方不断产生具有"前伸"、TBSS和假象回波结构的局地雹云超级单体回波群,这些飑前中小尺度系统是产生此次冰雹灾害的主要回波系统。(5)5 min风廓线雷达资料在前期阶段,能够观测到西南急流的演变情况,包括急流中的大风区。(6)当飑线系统临近时,受飑线中尺度环流的影响,飑线移动前方具有较强的上升运动,且伸展高度可以达到6000 m,但垂直速度、Cn^2和SNR都较小;当飑线系统过境时,具有很强的水平风切变,受到强降水的下曳作用,垂直速度、Cn^2和SNR都明显加大;飑线系统过境后,恢复到前期阶段。

By using the conventional observation data,disastrous loss data,AWS data,satellite infrared images,radar echoes and wind profiler products,a strong squall line process on 10 April 2012 was ana-lyzed with statistical analysis and feature extraction method.The results show that:(1)The squall line is tightly belt-shaped and composed of several tilt and deep convective cells.(2)The characteristics of me-soscal convective system (MCS)structure can be seen in FY2E infrared images.The sharp surface temper-ature front begins to form with MCS moving to east and precipitation cooling,moisture and heat transpor-ted by the southwest airflow and surface temperature rising.(3)Several parallel comb-shaped short-ribbon echoes appear and convection cells are continuously generated in the south side of the MCS.Finally they develop into a squall line echo belt in the earlier stage of the squall line system.(4)Local supercell hail storms with the structure of “front-extend”,TBSS and false echo are generated continuously ahead of the squall line,causing most of the damages during this hail process.(5 )The evolution of southwest jet stream including the gale area can be seen clearly in 5-min intervals wind profiler data in the early stage. (6)When the squall line system approaches,strong ascending motion ahead of the squall line can extend to 6000 m height influenced by the squall line mesoscale circulation,but the vertical velocity,Cn2 and SNR values are low.With the squall line passing,the horizontal wind shear is strong.Due to the dragging down action of strong rainfall,vertical velocity,Cn2 and SNR are significantly increased.After the squall line passes,all signals return to the initial phase.