一次渤海“切变线”诱发强对流天气监测及可预报性探讨

The monitoring and the study on a severe convective weather caused by warm shear line in the Bohai sea area

利用micaps3.2系统强对流实况监测、渤海6部天气雷达、海洋WRF模式等同步资料,对2015年8月31日渤海一次典型"暖式切变线"引发强对流天气过程进行综合分析及可预报性探讨。结果表明:天气尺度系统的有效配置为不同时段的中尺度对流系统发展提供了环流背景条件。08—20时渤海湾一线925—850 h Pa切变线东移增强,08时临近探空K指数35℃、SI指数-1.81℃及CAPE为166 J/kg,垂直风切变16 m/s,导致天津一线的强对流天气发生。20—02时低层925 h Pa"暖式切变线"北抬,20时K指数32℃,SI指数为1.36℃,CAPE达383 J/kg,垂直风切变为19 m/s,对流性不稳定能量增强,在渤海中部的切变线附近诱发多个中γ、β尺度强对流风暴单体,在雷达回波"列车效应"下,造成了秦皇岛近海新一轮强对流天气过程。WRF模式数值模拟与实况对比:对流有效位能(CAPE)08时初始场运行结果误差大于14时;逐小时强对流回波带演变与925 h Pa切变线和CAPE高值区较一致;强垂直运动和边界层水汽辐合触发CAPE的释放;在辽东湾北部Δθse(850—500 h Pa)较弱干冷切入与对流系统的发生、落区有一定对应关系;雷达监测网与WRF物理量叠加是提升海区强对流预警方法的有效途径之一。

Using the synchronous data such as weather radar, micaps 3.2, oceanic WRY model etc, the change of a typical severe convective weather process caused by warm shear line on 31 August, 2015 in the Bohai Sea was analyzed and its predictability was also be discussed. The results show that the effective configuration of the synoptic scale system can provide some circulation conditions for the development of the mesoscale convective system at the different time. The shear line moved eastward and enhanced at the 925 hPa and 850 hPa in Bohai Bay from 08：00 to 20：00, the index K was 35 ℃, index SI was -1.81%, the CAPE was 166 J/kg and the vertical wind shear was 16 m/s in the stratification curve at 08：00 A.M, because of these, the severe convective weather occurred in Tianjin. The warm shear line moved northward at the 925 hPa of the lower lay from 08：00 EM on August 31 to 08：00 A.M on September 1, index K was 32 ℃, index SI was 1.36℃, CAPE was 383 J/kg and the vertical wind shear was 19 m/s at 20：00 EM on September 1, the convective instability energy increased, several severe convective storm cell of meso-7 scale and meso-β scale near the shear line have been induced in the central area of Bohai Sea. Under the background of the conditions, more severe convective weather emerged above the coastal waters. After comparing the simulated results from WRF model and the observed data, the running error of the convection effective potential energy （CAPE） was less than 14 in the initial field at 08：00 A. M. The evolution of of the hourly echo strip from the strong convective system was corresponded with shear line of 925 hPa and the high value area of CAPE. The CAPE was released by the strong vertical movement and water vapor convergence of the boundary layer, being a smaller value of AOse （850-500 hPa） in north of Liaodong bay, and the cut-in of dry and cold has a certain correspondence with the occurrence and impact area of the convection system. Combined the radar monitoring network and physical quantity from WRF model could be one effective method for the warning of the severe convective system.