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

热带辐合带（ITCZ）海洋大陆巨型雷暴的国际研究及其对全球电路的贡献

基本信息

批准号：
14254001
负责人：
KAWASAKI Zen-ichiro
金额：
$ 25.04万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

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

本报告致力于实现用于雷暴观测的可操作 VHF 宽带数字干涉仪（DITF） VHF 宽带 DITF 是一种用于定位 VHF 频段闪电进展引起的宽带脉冲电磁波源的系统。脉冲不仅提供了雷电行进通道的图像，还提供了雷云内部的电荷分布。基于VHF宽带数字干涉技术的显着特点，开发了一种新型闪电定位和监测系统。宽带 DITF 是其超宽带和隐式冗余，用于估计 VHF 脉冲源的位置。宽带数字干涉仪的示意图是计算两个适当分离的天线捕获的电磁信号之间的相位差，并将此过程应用于每个傅里叶分量。由于众所周知，一次闪电主要从击穿尖端发出数千个 VHF 脉冲，因此其源的位置相当于对闪电通道发展进行成像。在开发过程中，我们安装了一个实验系统并进行了闪电观测的现场活动。讨论了 VHF 宽带 DITF 的准确性或误差估计，以验证其性能，并采用计算方法来计算电磁场，并验证了所提出技术的有效性。将实验DITF获得的结果与摄像机、经典窄带干涉仪、气象雷达等的观测结果进行比较，并讨论了色散、傅立叶分量和相互作用方面的误差评估。VHF宽带的使用。提出了研究雷云内部电荷分布的 DITF 案例研究，重点关注冬季雷暴季节期间的正 CG 闪光、雷云内部正电荷的高度和数量、J 或 K 过程以及先导级数，尤其是负 CG 的启动。还尝试了基于电子技术的最新进展来开发先进的系统，以获得高性能的卫星上的VHF宽带DITF。随后发表了有关该系统的论文。这项研究的结果列出较少。