International research on maritime continent giant thunderstorms in intertropical convergence zone(ITCZ) and their contribution to the global electric circuit

本文致力于实现一台用于雷暴观测的VHF宽带数字干涉仪(DITF)。VHF宽带DITF是一种用来定位VHF频段闪电行进引起的宽带脉冲电磁波来源的系统。基于VHF宽带数字干涉测量技术，研制了一种新型的闪电定位监测系统。VHF宽带DITF的显著特点是其超宽带和隐式冗余，用于估计VHF脉冲源的位置。宽带数字干涉仪的原理是计算由两个适当间隔的天线捕获的电磁信号之间的相位差，并将该过程应用于宽带电磁脉冲的每个傅立叶分量。因为众所周知，一道闪电发出几千个…更多的VHF脉冲主要来自击穿的尖端，其来源的位置相当于成像闪电通道的发展。作为开发的第一步，我们安装了一个实验系统并进行了闪电观测的野外战役，讨论了甚高频宽带DITF的精度和误差估计，以验证其性能。给出了一种计算电磁场的方法，并用数值方法验证了该方法的有效性。将实验得到的DITF与摄像机、经典窄带干涉仪、天气雷达等观测结果进行了比较。讨论了色散、傅里叶分量和相互作用对误差的影响，提出了利用VHF宽带DITF研究雷云内部电荷分布的方法。对冬季雷暴季节的正CG闪电、雷云内部正电荷的高度和数量、J-或K-过程以及引导性进展特别是其引发的负CG闪电进行了个例研究。对雷暴的实时监测也进行了尝试。先进的系统是在电子技术最新进展的基础上发展起来的，以获得高性能。卫星上的甚高频宽带DITF也正在规划中。然后列出了关于这一研究成果的已发表论文。较少

This report is devoted to realize an operational VHF broadband digital interferometer(DITF) for thunderstorm observations. The VHF broadband DITF is a system to locate the source of a wideband impulsive EM wave caused by lightning progression in VHF band. The source locations of the VHF impulses provide not only the image of lighting progression channel but also the charge distribution inside thunderclouds.A new type of lightning location and monitoring system has been developed based on a technique of VHF broadband digital interferometry. The remarkable feature of the VHF broadband DITF is its ultra-wide bandwidth and implicit redundancy for estimating the location of a VHF impulse source. The schematic of broadband digital interferometery is calculating phase difference between EM signals captured by two properly separating antennas, and this procedure is applied to each Fourier component of broadband EM pulses. Since it is well known that one lightning flash emits a few thousands of … More VHF impulses mainly from the tip of breakdown, the location for their sources are equivalent to imaging the lightning channel development. As a first step of the developing, we install an experimental system and conduct field campaigns for lightning observations.The accuracy or error estimation of the VHF broadband DITF is discussed to validate the performance. A computational approach is carried out calculating the EM fields and the effectiveness of the proposed technique is demonstrated numerically. The obtained by the experimental DITF are compared with observations by video camera, classical narrowband interferometer, weather radar, and so forth. The error evaluations in terms of dispersions, Fourier components, and interactions are also discussed.The use of the VHF broadband DITF to study charge distribution inside thunderclouds is proposed. Case studies focused to positive CG flashes during winter thunderstorm season, the altitude and the quantity of positive charges inside thundercloud, J- or K- processes, and the leader progressions especially its initiation of negative CG flashes are implemented. Real-time monitoring of thunderstorm is also attempted. The advanced system is developed on the recent progress of electronics to obtain highly performance. A VHF broadband DITF on board a satellite is being planed as well.Then the published papers about the results of this research are listed. Less