Observation and preliminary analysis on the attachment process of lightning flashes striking on high structures

A field observation experiment of lightning flashes occurring on high structures was conducted in the summer of 2009, at Guangzhou, Guangdong Province, China. Two downward negative lightning flashes, which stroke on high structures and are numbered as L01 and L02, have been analyzed in this paper. L01 stroke on a TV Tower with a height of 610 m and L02 on a structure with a height of 432 m. The preliminary analysis shows that: both lightning discharges exhibit long upward connecting leader with their lengths of longer than 450 m for L01 and of about 177 m for L02, respectively; the upward-moving leader of L01 only has a single channel, while that of L02 has two branches; for each event the average 2D progression velocity of upward-moving leader is of the order of 10⁵ m/s; and there are no obvious difference between the 2D progression velocities of the upward-moving leader and the downward-moving leader during the last several hundreds of microseconds before the return stroke.