Rocket-triggered lightning propagation paths relative to preceding natural lightning activity and inferred cloud charge

摘要

Lightning Mapping Array (LMA) data are used to compare the propagation paths of seven rocket-triggered lightning flashes to the inferred charge structure of the thunderstorms in which they were triggered. This is the first LMA study of Florida thunderstorm charge structure. Three sequentially (within 16min) triggered lightning flashes, whose initial stages were the subject of Hill et al. (2013), are reexamined by comparing the complete flashes to the preceding natural lightning to demonstrate that the three rocket-triggered flashes propagated through an inferred negative charge region that decreased from about 6.8 to about 4.4 km altitude as the thunderstorm dissipated. Two other flashes were also sequentially triggered (within 9 min) in a thunderstorm that contained a convectively intense region ahead of a stratiform region, with similar observed results. Finally, two unique cases of triggered lightning flashes are presented. In the first case, the in-cloud portion of the triggered lightning flash, after ascending to and turning horizontal at 5.3 km altitude, just above the 0 degrees C level, was observed to very clearly resemble the geometry of the in-cloud portion of the preceding natural lightning discharges. In the second case, a flash was triggered relatively early in the storm's lifecycle that did not turn horizontal near the 0 degrees C level, as is usually the case for triggered lightning in dissipating storms, but ascended to nearly 7.5km altitude before exhibiting extensive horizontal branching.