2017.6.21致灾雷暴大风特征分析

The Disastrous Thunderstorm and Gale on June 21, 2017: Characteristics Analysis

为深入探讨保定雷暴大风的形成机理和提前预防农业气象灾害的发生,本研究利用常规观测资料及NCEP/NCAR逐日6 h再分析资料,对2017年6月21日发生在保定东部及雄安新区的雷暴大风天气进行分析。结果表明:地面中尺度辐合线和冷池是直接触发机制;探空曲线存在上下2个自由对流高度LFC;雷暴大风出现在最强负变温与正变压前侧锋区;雷暴大风位于高能舌附近的能量锋区;边界层弱冷平流有利于水平锋区的形成与加强。整层MPV2负值的增大、高低空垂直螺旋度的耦合,构成此次雷暴大风天气的典型模式。此次过程是发生在高空槽前的雷暴大风天气,高低空系统的配置和不稳定条件比较有利于强对流的发生。依据地面中尺度系统至少可以提前10^20 min发出预警信号。

To further explore the formation mechanism of thunderstorm and gale in Baoding and to prevent the occurrence of agrometeorological disasters in advance, based on the conventional observation data and daily NCEP/NCAR reanalysis data of 6 h, we analyzed a thunderstorm and gale occurred in eastern Baoding and Xiong’an on June 21, 2017. The results showed that: the mesoscale convergence line and cold pool were the direct trigger mechanism;there were two free convection heights(LFC) in Beijing T-ln P;the thunderstorm and gale was prone to trigger in the front area of the strongest negative temperature and positive pressure;the thunderstorm and gale was near the tongue of high energy;weak cold advection in the boundary layer was beneficial to the formation and strength of the horizontal front;the increase of negative values of MPV2 in the whole layer and the coupling of vertical helicity between high and low constituted the typical mode of the thunderstorm and gale. The gale was in front of high trough, the coordination between weather systems at the upper and lower troposphere together with instability conditions were very beneficial to the development of severe convective weather. According to the ground mesoscale system, warning signals could be sent at least10-20 minutes in advance.