华北地区雷暴云内电荷结构和闪电放电过程的探测实验研究

The charge structure inside the thunderstorm not only determines initiation, propagation and characteristics of lightning discharges, it effects on electron density and potential of the ionosphere as well. This project will take advantages of the self-developed electric field vector sounding technique to detect the 3D electric field inside the thunderstorm by conducting the balloon-borne electric field sounding experiment in Northern China, and the vertically stacked charge regions inside the thunderstorm will be deduced quantitatively based on the electric field profiles by combining the 1D approximation of Gauss's law with additional information from 3D patterns in the electric field vectors in the storms. The Beijing Lightning location NETtwork（BLNET）and short-baseline 2D VHF/UHF Lightning Mapping Interferometer (LMI) with high resolution will be coordinately used to study the lightning physical processes, and to determine the charge distribution of both positive and negative polarity involved in the discharges. Combining with the Doppler dual linear polarization Radar data and mesoscale 3D thunderstorm numerical simulation, the charge distribution inside the thundercloud and corresponding lightning discharge processes will be revealed, including that in different developing stage of the storm, that within vigorous convection region and nearby, and in the stratiform region of the thundercloud. The project will also focus on the thermodynamic and microphysical aspects which cause the different charge structure and lightning activity in different thunderstorms, especially the convection regimes and environmental factors on which the inverted-charge structure depends. The thunderstorm charge distribution is one of the frontier questions related to atmospheric electricity, and the research results of this project are significant not only for thunderstrom electricity, but also for enhancement the capability of simulation and short term forecasting of the disasturous thunderstorm, and it will aslo provide important information on the ionesphere physics researches.

雷暴云内的起电和电荷结构不仅决定着闪电的发生发展，同时也影响电离层电子浓度和电位。本项目利用自行研制的雷暴云双球三维电场探空技术，通过华北地区雷暴云内的钻云探空实验，定量确定雷暴云内电荷分布的垂直结构；利用多频段闪电辐射源三维定位系统(BLNET)和高分辨率闪电VHF/UHF干涉仪二维图示系统(LMI)，详细研究闪电放电物理过程，确定与放电有关的云内正、负电荷分布；结合多普勒双偏振雷达资料和中尺度三维雷暴云模拟，系统研究不同雷暴云中的电荷分布特征，揭示雷暴不同发展阶段、强对流区内外以及层云降水区的电荷结构和闪电特征，阐明电荷结构对闪电放电过程的影响；揭示不同雷暴云电荷结构和闪电差异的动力和微物理成因，特别是反极性电荷结构所依存的雷暴条件和环境因素。研究结果不仅对雷暴电学研究有重要的科学意义，对改进灾害性雷暴数值模拟和预报水平也有重要的应用价值，同时对电离层空间科学研究也有启示意义。

雷暴云内电荷分布不仅决定闪电的发生发展、类型和强度，也通过传导电流、闪电等影响电离层电子浓度和电位。项目通过发展和完善探测技术和平台，开展观测实验，获得了雷暴云电荷结构和闪电活动的创新认识。基于自主研发的雷暴云电场探空系统，克服雷暴条件下开展探空实验的困难，通过穿雷暴云原位探测，获得宝贵的云内电场和温湿廓线；发展解算方法，得到云内探空路径上的垂直电荷分布；实现对闪电通道和放电过程可分辨的高精度三维动态定位成像，据此，遥感得到云内正-负-正或反极性的主要电荷区域。研究揭示云内不同电荷分布对闪电的影响，相反极性电荷区的水平配置可导致双极性闪电，雷暴消散阶段层云区域的大范围正电荷区易产生正地闪，并触发高塔上行闪电。射频定位-高速摄像-电磁场探测等多探测手段结合，揭示正先导不连续发展的本质以及正、负先导发展的异同；发现闪电连接过程最后一跳的瞬间精细结构和公共流光区主导流光路径的优势增长机制；提出正先导通道分叉的两种模式，即悬浮空间双向先导与主通道连接分叉和主通道头部直接分裂分叉。通过增加电场力对动力和微物理场的反馈，改进耦合起电放电过程的三维雷暴云模式，发现电场力影响霰、雹粒子下落末速度，并对云内起电和闪电有正反馈作用。综合利用观测和数值模拟，研究飑线、多单体雹暴、超级单体的闪电活动和演变特征，揭示其云内复杂的电荷结构和热动力-微物理过程的影响；发展改进模式动力场的闪电资料同化新方法，提升了对强对流和降水的预报效果。已发表论文40篇，其中Geophys Res Lett，J Geophys Res等发表SCI论文29篇，另有3篇在审；获授权专利2项。项目获得宝贵的雷暴云内电场和温度、湿度等第一手原位探测资料，闪电三维动态定位和高速摄像等资料。研究结果不仅对大气电学发展有科学意义，对空间电学研究有参考价值，也对改进灾害性雷暴数值模拟和预报水平、雷电灾害防护和人工干预等有应用价值。