Infrared and Visible-Range Optical Observations of Lightning at LOG (Lightning Observatory at Gainesville) and Associated Modeling

闪电是一种瞬间的、高电流的放电，通常在空气中以每秒数十到100安培的速度闪光。闪电通道由电离气体或等离子体组成，其峰值温度通常为3万摄氏度，大约是太阳表面温度的五倍。美国每年大约发生2500万次云对地闪电放电，由于21世纪全球变暖，这一数字预计将增加约50%。对没有防护的物体或系统的雷击可能是灾难性的。闪电造成的死亡人数比龙卷风和洪水等任何其他与雷暴有关的灾害都要多。雷电引发了许多森林火灾，超过30%的电力线路故障与雷击有关。在这项受资助的研究中，位于佛罗里达州盖恩斯维尔的闪电观测站将首次使用新的高速红外(IR)成帧相机与现有仪器一起进行闪电观测，这些仪器包括在不同频率范围运行的光学系统、电场和磁场测量系统以及X射线探测器，以获得以前从未可能获得的闪电过程的图像。红外相机将允许对云中的闪电通道进行成像，而这些通道通常是可见光相机无法访问的。研究了闪电通道的冷却过程和通道不同部位的热能输入。光学和相应的全球定位系统时间戳电磁场数据将首次用于开发一个非线性和非均匀分布电路模型，该模型将能够调查各种闪电过程，包括与地面或接地物相连的闪电的最后跳跃阶段，这是天然闪电尚未记载的。这项资助的研究将进一步促进我们对闪电物理及其影响的理解，对环境和气候变化研究以及减轻雷击对人、结构和系统的危害具有重要意义。需要更多地了解雷电连接过程，以设计适当的防雷保护措施，并制定雷电测试标准。该项目将涉及博士后和博士后研究生，以及国际合作，包括两名由本国大学支持的访问学者和一名富布赖特学者。这项研究成果将被纳入广受欢迎的佛罗里达大学高级本科生/研究生课程《闪电》。PI将继续参与高中科学教育和公众对雷击危险的认识。除了物理和动力气象学领域外，该项目的成果还将用于其他学科，包括高能大气物理、等离子体物理、雷电防护和测试以及雷电安全。

Lightning is a transient, high-current electric discharge of typically tens of kiloamperes in air with a flash rate in tens to a hundred per second. Lightning channel is composed of ionized gas or plasma, whose peak temperature is typically 30,000o K, about five times higher than the temperature of the surface of the Sun. Each year, some 25 million cloud-to-ground lightning discharges occur in the United States, and this number is expected to increase by about 50% due to global warming over the 21st century. A lightning strike to an unprotected object or system can be catastrophic. Lightning causes more fatalities than any other thunderstorm-related hazard, such as tornadoes and flooding. Lightning initiates many forest fires, and over 30% of all electric power line failures are lightning related. In the funded research, a new high-speed infrared (IR) framing camera will be employed for the first time at the Lightning Observatory in Gainesville, Florida for lightning observations in conjunction with the existing instrumentations, including the optical systems, electric and magnetic field measuring systems operating in different frequency ranges, and x-ray detector to obtain a view of lightning processes that has never been possible before. The IR camera will allow the imaging of lightning channels inside clouds that generally are not accessible to visible-range cameras. The lightning channel cooling process and the thermal energy input to different parts of the channel will be studied. The optical and corresponding GPS time-stamped electromagnetic field data will be used to develop, for the first time, a non-linear and non-uniform distributed-circuit model, which will allow the investigation of a variety of lightning processes, including the final-jump phase of lightning attachment to ground or grounded object, which has not been documented for natural lightning. This funded research will further advance our understanding of the physics of lightning and its effects with important implications for environmental and climate change research and for mitigation of lightning hazards to people, structures, and systems. An improved knowledge of lightning attachment process is needed for designing adequate protection against lightning and for developing lightning testing standards. This project will involve postdocs and Ph.D. graduate students, as well as international collaborations, including two visiting scholars supported by their home Universities and a Fulbright Scholar. The research findings will be incorporated in the popular University of Florida senior undergraduate/graduate course "Lightning." The PI will continue to engage with high-school science education and public awareness of lightning hazards. Besides the Physical and Dynamical Meteorology area, the results of the project will be useful in other disciplines, including high-energy atmospheric physics, plasma physics, lightning protection and testing, and lightning safety.