云内先导发展对正地闪放电过程的影响研究

正地闪不仅对直接击中的地面目标物造成强烈的破坏，产生的瞬时强电场变化还能够引发高建筑物上行闪电，以及雷暴上方的中高层瞬态发光事件。正地闪回击前后经常伴有长时间的云内活动，由于正地闪发生频率低、放电过程复杂、正先导辐射强度弱，关于云内先导发展对正地闪放电过程的影响，目前认识还很有限。本项目拟基于北京闪电综合探测平台已有的先进设备开展高分辨率的光电同步综合观测，包括高速光学、多频段电场、甚高频闪电干涉仪、低频快天线定位网等多种探测手段，建立正地闪综合探测数据集；归纳正地闪的放电类型，分析不同类型正地闪的云内起始位置和先导发展传输特征；探索下行正先导如何从云内始发并接地产生首次回击，以及回击后云内先导如何发展产生罕见的继后回击、触发高建筑物上行闪电等。研究结果不仅对于揭示云内先导发展影响正地闪放电过程的特征和机制有着重要的科学意义，对于设计更好的雷电防护系统也有着重要的实际应用价值。

Positive cloud-to-ground (+CG) lightning not only causes strong damage to the ground target that is directly struck, but also causes transient strong electric field changes to trigger tower-initiated upward lightning, as well as transient luminous events above thunderstorms. A long-term in-cloud lightning activities is often appeared before and after the positive return stroke. Due to the low occurrence frequency of +CG lightning, complex discharge processes, and weak radiation emitted by the positive leader, there is limited understanding about the impact of propagation and development of in-cloud leader on the +CG discharge process. This project is intended to take advantage of the existing advanced equipment of the Beijing lightning comprehensive detection platform, including high-speed camera, multi-frequency electric field detection, very high frequency (VHF) lightning interferometer, and low-frequency fast antenna lightning location network, to establish a comprehensive detection dataset of +CG. Then summarize the discharge types of +CG lightning, and analyze the inception positions and developing characteristics of their in-cloud leaders. The program will explore how the downward positive leader incept from the cloud and produce the positive return stroke (+RS), and how the propagation of in-cloud leader induce the uncommon subsequent +RS and tower-initiated upward lightning, etc. The results of the study not only have important scientific significance for revealing the characteristics and mechanisms of the in-cloud leader development that affects the +CG discharge process, but also have significant practical application value for designing better lightning protection system.