High-Speed Video and Electrical Study of Upward Lightning Triggered by Towers

点击翻译按钮获取中文摘要

This research will address how lightning is triggered and propagates upward from tall structures such as buildings and towers. Existing literature and previous observations suggest that nearby flashes can create conditions favorable for upward leader initiation from tall objects. The objective of these investigators is to quantify and understand these conditions and deter-mine a triggering flash component responsible for upward leader initiation. A combination of electromagnetic and optical sensors will record upward lightning flashes from multiple transmission towers near Rapid City, South Dakota. Electromagnetic sensors will include electric field meters, fast and slow field change sensors, and two interferometers. Operation of these sensors will be coordinated with high-speed video, standard-definition video, and digital still image cameras. Observations made with these assets will be analyzed along with National Lightning Detection Network (NLDN) and meteorological data (i.e., radar, satellite, thermodynamic sounding and meteorological surface parameters) to determine types of flashes and their properties that affect or are critical for the initiation of upward leaders from tall objects, storm type, region and stage of development during which upward lightning occurs, and the conditions for triggering upward leaders on multiple tall objects during the same flash.The intellectual merit of this research is centered upon a more complete physics-based understanding of mechanisms involved in triggering and propagation of lightning channels that are unique to strikes on tall structures. Broader impacts of this effort will include collaborative interactions with lightning researchers based in Brazil, who will participate in the South Dakota-based field program, through enhanced graduate student and undergraduate-classroom training in the methodology and interpretation of a diverse set of field observations and associated data analysis techniques, and through dissemination of these findings via conferences and in the peer-reviewed literature. Findings from this research will benefit society through increasing understanding of and protection from potentially hazardous effects of lightning strikes to both occupants and equipment mounted on high-rise buildings and other tall structures utilized for telecommunications and energy production. In addition, presentations related to this research will be made to regional elementary and secondary schools, and service clubs/organizations to increase lightning awareness and stimulate interest in higher education and atmospheric research.