Measurement of Cloud-to-ground and Spider Leader Speeds with High-speed Video Observations
From analysis of digital high-speed video records of flashes in south and southeastern Brazil, the average speeds of positive and negative leaders of cloud-to-ground and spider lightning were estimated for the first time in Brazil. All flashes were recorded with a Redlake MotionScope 8000S (1,000 frames per second, 1.0 ms of exposure time and 2.0 sec of recording time) and a Photron Fastcam 512 PCI (up to 8,000 frames persecond, 125 μ s of exposure time and 2.0 sec of recording time), both high-speed cameras were synchronized with GPS. The frame rate used allows the measurement of the speeds with good accuracy. The Brazilian Lightning Location System covered the areas of observation (south and southeastern Brazil) was used to determine the polarity and the distance of the observed lightning flashes. As far as we know, although there are several published measurements of leader velocities for negative cloud-to-ground flashes, there is only one cloud-to-ground positive leader speed published by Berger and Vogelsnager in 1966. This work shows that the speed of positive leaders is not much different from negative stepped leader speeds for cloud-to-ground flashes and from spider leader speeds. These results are compared to other results from past studies done in different regions of the world.
Marcelo M. F. Saba Leandro Z. S. Campos Maurício G. Ballarotti Osmar Pinto Jr
National Institute for Space Research – INPE, S. José dos Campos, SP, P.O. Box 515, 12201-970, Brazil
国际会议
第13届国际大气电学会议(The 13th International Conference on Atmospheric Electricity)
北京
英文
2007-08-13（万方平台首次上网日期，不代表论文的发表时间）