闪电初始击穿过程电荷传输特征的观测研究

How lightning is initiated inside storms is a long-standing but fundamental question in lightning community. Lightning discharges typically start with a preliminary breakdown stage which is characterized by a train of bipolar pulses in electric field change records. A local network comprising of six short-spaced stations will be deployed to continuously record electrostatic fields and VLF/LF electric field produced during the preliminary breakdown process. The initial leaders of preliminary breakdown are inferred by obtaining 3-D locations with high precision for initial pulses during PB stage. After that, the charge transfer along the leader channel will be obtained from electrostatic field recorded at multiple stations. The results obtained in this project are sure to enrich knowledge regarding lightning initiation.

长期以来闪电在云内如何启动是困扰学术界的基础问题。通常认为闪电由双极性脉冲为特征的初始击穿过程启动。本项目申请以获取闪电初始击穿通道内电荷输送特征为目标，为此建设一个由6个高精度GPS时间同步子站构成的闪电地面电场快、慢变化和VLF/LF辐射场联合观测系统，利用低频干涉技术研究初始击穿先导云内发展通道，并以此为约束利用多站观测的地面静电场资料反演先导通道内电荷传输特征。本项目研究结果将弥补学术界对闪电初始先导传播过程中电荷输送特征的认识不足，结果将丰富学术界对闪电初始击穿过程的认识。

本项目研究针对闪电云内放电过程尤其是初始击穿过程的传输电荷反演需求，建设了一套包括八个子站的广州地面电场变化观测阵列用于不间断记录雷暴放电的地面静电场变化，并成功取得了一批闪电观测资料。包括初始击穿过程在内的云内放电过程的电荷传输特征研究将在2022年展开。同时，利用江淮天电阵列观测的历史闪电波形资料，通过与空基的光学资料进行对比，首次发现了雷暴云顶之上的蓝色发光事件与强对流雷暴上层发生的一类负NBE事件紧密关联，进一步与国际空间站观测的蓝色辐射的时变波形进行对比，首次证实这些中层大气蓝色发光事件与强对流雷暴中上部的NBE事件物理同源,因此有望通过地基的天电观测实现对中层大气放电的连续监测。同时发展了基于卷积神经网络对闪电波形进行类型识别的方法。