山东半岛秋季一次脉冲风暴下击暴流观测分析

利用山东威海CINRDA/SA多普勒雷达探测资料，结合常规天气图资料、地面自动气象观测站资料等，对2018年9月8日发生在威海文登机场附近的一次下击暴流天气特征进行分析。结果表明：1)此次下击暴流天气发生在高低空一致的西北气流背景下，午后太阳辐射使得低空大气加热显著，形成了强烈的不稳定层结。2)大气层结特征呈喇叭状温湿分布，850 hPa以下接近干绝热的温度直减率，为下击暴流的发生提供了有利环境条件。3)地面辐合线为风暴单体的产生提供了动力抬升条件。4)从多普勒雷达产品上看，风暴初始回波发生在午后海风锋触发的晴空窄带回波上，通过单体间的合并加强，发展成为多单体风暴；下击暴流出现前，对流风暴回波强度及高度明显发展，成熟阶段的对流风暴伴有回波悬垂结构和三体散射特征，伴随着强反射率因子核心的持续下降，下击暴流迅速到达地面，径向速度图上存在明显的中层辐合、旋转、低层辐散的现象；5 km以上60 dBZ强反射率因子核心的下降，结合径向速度中层辐合、低层辐散特征可提前3～9 min预警下击暴流的发生。

Observational analysis of downburst by a pulse storm in autumn in Shandong Peninsula

Based on data from Weihai CINRDA/SA Doppler radar, combined with conventional meteorological data and data from ground automatic meteorological stations, the characteristics of a downburst weather event near Weihai International Airport on 8 September 2018 are analyzed. The results are shown below. 1) The downburst occurs in the northwest airflow background consistent at high and low altitudes, and solar radiation makes the low-altitude atmosphere heated significantly in the afternoon, forming a strong unstable stratification. 2) The trumpet-shaped distribution of vertical temperature and humidity and the temperature lapse rate approaching the dry adiabatic below 850 hPa are favorable environmental conditions for the occurrence of downburst. 3) The presence of ground convergence lines provides dynamic uplifting conditions for the generation of storm cells. 4) From the Doppler radar products, the initial echo of the storm occurred on the clear sky narrow-band echo by the midday sea breeze front, and then the single-cell storm merged and developed into an isolated multi-cell storm; before the downburst, the intensity and height of convective storm echoes developed obviously, convective storm in mature stage was accompanied by echo overhanging structure and three-body scatter characteristics, the downburst quickly reached the ground with the continuous decline of the core of the strong reflectivity factor, and there were obvious convergence and rotation in the middle layer and divergence in the lower layer on the radial velocity map; the gradual decrease of the core of the 60 dBZ reflectivity factor above 5 km and the characteristics of radial velocity (convergence in the middle layer and divergence in the lower layer) can be used to predict the occurrence of downburst three to 9 minutes in advance.