A review of positive and bipolar lightning discharges

TLDR: In this article, the characteristics of positive and bipolar lightning discharges are reviewed and five situations that appear to be conducive to the more frequent occurrence of positive lightning are discussed, including dissipating stage of an individual thunderstorm, winter thunderstorms, trailing stratiform regions of mesoscale convective systems, some severe storms, and 5) thunderclouds formed over forest fires or contaminated by smoke.

Abstract: Characteristics of lightning discharges that transport either positive charge or both positive and negative charges to the ground are reviewed. These are termed positive and bipolar lightning discharges, respectively. Different types of positive and bipolar lightning are discussed. Although positive lightning discharges account for 10% or less of global cloud-to-ground lightning activity, there are five situations that appear to be conducive to the more frequent occurrence of positive lightning. These situations include 1) the dissipating stage of an individual thunderstorm, 2) winter thunderstorms, 3) trailing stratiform regions of mesoscale convective systems, 4) some severe storms, and 5) thunderclouds formed over forest fires or contaminated by smoke. The highest directly measured lightning currents (near 300 kA) and the largest charge transfers (hundreds of coulombs or more) are thought to be associated with positive lightning. Two types of impulsive positive current waveforms have been obse...