基于综合观测和数值模拟研究城市化对雷暴对流结构和闪电活动的影响机制

The structural changes of the underlying urban surface and the boundary layer in the metropolis region are prone to cause the local thermal condition and dynamic distribution, and form a strong and destructive thunderstorm which often causes extreme weather events. The urban effect influence not only the convective development, dynamic structure and microphysical process within the thunderstorm, but also the charge structure and the lightning activity of the thunderstorm. At present, the comprehensive study of dynamic-microphysics-electrification is less considered. Considered the “Jing-jin-ji” region with comprehensive observation as the research area, based on the three-dimensional lightning detection network (BLNET), radar, and the three-dimensional thunderstorm model, the evolution of convective structure and corresponding lightning activities of thunderstorms will be explored. Through the comparison of the observation, the difference of the convective structure and lightning activities in various types of thunderstorms under the urban effect is discussed. By multi-group sensitivity test, we investigate the contribution of urbanization effect including dynamical, thermal and cloud condensation nuclei to the convective initiation, development and electrification of thunderstorm. It will be focused on the convective initiation of abrupt thunderstorm and the indicative function to the lightning evolution on the strong convection. The research results not only enhance the relationship between the thunderstorm structure and the lightning activity, but also provide the practical significance for improving the severe convective weather forecasting.

城市区域内由于局地地形、复杂的城市下垫面和边界层结构使得局地热、动力不均匀分布，易形成组织性强、破坏力大的雷暴天气系统。城市作用不仅影响了雷暴内的对流发展、动力结构、微物理过程，而且改变了云中电荷结构和闪电活动。目前考虑了城市群背景下雷暴的动力-微物理-电活动特征的综合研究较为欠缺。本项目以京津冀地区为研究的目标区域，基于北京闪电定位网（BLNET）、雷达、地面气象要素等多种观测手段，同时利用中尺度雷暴云模式，研究城市化背景下不同类型雷暴整体结构的演变及其对应的闪电活动特征。通过多组敏感性试验，探讨城市动力、热力效应以及城市云凝结核对雷暴初生、发展演化和起电过程中的贡献机制，并与实际观测进行对比验证。重点关注城市区域内突发性雷暴的触发机制以及闪电演变特征对强对流的指示作用，研究结果将增进对雷暴云结构与闪电活动之间关系的认知，并对提高雷暴的降水预报也将有重要的实际应用价值。

随着城市化进程的加快，使得城市背景下发生的对流系统具有更大的破坏力和危害性。对强对流活动和极端灾害性天气的预警、预报要求也越来越高。城市效应不仅影响了强对流的触发和发展，也影响了对流云内电荷结构和闪电活动。深入的认识城市背景下不同类型雷暴特征以及城市效应对强对流天气系统的影响机制，不仅可以提高灾害性雷暴天气的短时临近预报水平具有重要的实际应用价值，并且对雷暴气象学和大气电学的深入研究具有重要的科学意义。本项目依托京津冀地区开展的集合闪电三维定位、雷达和地面探测的强对流天气和闪电活动的综合观测，并结合高精度中尺度数值模式，通过观测和模拟相结合的手段，对城市背景下强对流天气系统进行了深入分析，取得如下重要研究进展：获得了城市背景下不同类型雷暴系统中闪电活动特征及差异；进一步揭示了线状对流系统中闪电活动与动力结构、微物理过程之间的关系；获得了雷暴不同区域内水成物粒子信息与闪电活动的分布特征；通过分析沙尘对雷暴的影响机制发现了沙尘-雷暴中特殊的电荷结构；揭示了城市气溶胶对雷暴动力结构、微物理过程和电荷结构的影响；发现在气溶胶影响下，首次闪电发生推迟；得到了闪电频数跃增对强对流灾害性天气现象的预警作用。研究结果不仅提高了对城市背景下触发对流系统的科学认识，增进了气溶胶对雷暴电荷结构影响的理解，也为强对流天气的预警、预报提供参考。