Initial Electric Field Changes of Lightning Flashes in Two Thunderstorms

Abstract:

In a study of lightning initiation, Marshall et al. [2014, JGR Atmospheres] found that an initial electric field change (IEC) occurred before the initial breakdown (IB) pulses in 18 cloud-to-ground (CG) flashes and in 18 intracloud (IC) flashes. Because the IECs were small in amplitude and slowly developing (i.e., primarily electrostatic events), they were only detected by sensors within the reversal distance of each flash. In this presentation we report on a search for IECs in two small Florida thunderstorms that occurred close to several E-change sensors. One storm had 57 flashes; the other had only 13 flashes. The key result is that 69 of the 70 flashes began with detectable IECs. For the one flash without a detectable IEC, the closest sensor was at the reversal distance, presumably masking the IEC. Three of the flashes analyzed seemed to begin twice, in the sense that they had two sets of IB pulses; each beginning was preceded by an IEC.