飑线回波结构与环境风垂直切变的关系

为研究春季和夏季的环境风垂直切变对飑线结构的影响,结合雷达、卫星及探空资料,重点分析了2014年7月27日浙江宁波地区飑线过程的天气背景和不稳定能量垂直结构特征,揭示了产生飑线天气的先兆信息。为进一步研究飑线的回波结构与环境风垂直切变的关系,利用雷达回波的垂直剖面图,对比分析了20140727飑线与20140319台州飑线个例的垂直结构,发现在浙江地区,春季飑线强回波主体有向环境风方向倾斜的趋势;而夏季个例强回波主体无倾斜。暖空气入流上升后的出流方向受高空环境风的影响,春季高空风强,风速垂直切变大,入流上升后在风暴高层向前部出流,类似于中纬度引导型飑线的结构;夏季高空风弱,风速垂直切变小,入流气流上升后向风暴高层的后部出流,类似于热带传播型飑线的结构。为了改进飑线的临近预报水平,计算了20140727飑线的径向散度场。结合回波强度和速度分析飑线的辐合区,可以更准确地预测强对流的位置,揭示回波的生消演变。研究结果有助于深入理解飑线回波结构与环境风垂直切变的关系。

Relationship between the structure of squall line and environment wind vertical shear

The relationship between the structure of the squall line and environment wind vertical shear is the important issue. The weather background and the instability energy vertical structure of the squall line occurred on July 27,2014 in Zhejiang ningbo is emphatically analyzed using the radar,satellite,and sounding data,revealing the portent information of squall line.For further research on the relationship between the echo structure of the squall line and environment wind vertical shear,comparing and analyzing the vertical structure of the squall line occurred on Mar 19,2014 in Zhejiang taizhou with radar vertical cross-sectional structure shows that in Zhejiang area, the spring squall line echo subjects to environment wind direction while that of summer no tilt, and the direction of upper updraft divergence flow after warm air rising is affected by the environment wind in a higher level.The spring environment wind in a high level is always strong, wind vertical shear value is high,warm air flow after rising output in the front of storm,similar to the structure of the mid latitude steering-level squall line type.The summer environment wind is weak, wind vertical shear value is low,the updraft output to the rear of the storm,the structure is similar to the tropical propagating squall line type. In order to improve the level of nowcasting of squall line,the convergence obtained by radar echo and calculating radial divergence of 20140727 squall line analyzing, can predict the location of strong convection more precisely, reveal the evolution of echo.The results help to understand the relationship between the structure of squall line and environment wind vertical shear deeply.