Relationships among Narrow Bipolar Events, "total" lightning, and radar-inferred convective strength in Great Plains thunderstorms

Abstract

Narrow Bipolar Events (NBEs) are a recently discovered distinct class of intracloud lightning discharges whose associated processes produce the most powerful very high frequency (VHF) radiation observed from lightning. NBEs are thus the prime candidate for proposed satellite-based VHF global lightning mapping and storm tracking missions. In this study, we offer a detailed evaluation of the Great Plains Los Alamos Sferic Array (LASA). We then statistically compare NBE rates to non-NBE lightning rates measured by both the LASA and the National Lightning Detection Network (NLDN) and to NEXRAD radar-infeffed metrics of convective strength for thunderstorms in the Great Plains from May to July 2005. We find strong correlations between total lightning rate and convective strength, especially in terms of the height of 30 dBZ radar echo. However, we find much weaker correlations between NBE rate and non-NBE lightning rate and between NBE rate and radar-inferred convective strength. Though NBEs occur in the same storms as other lightning, they cluster more closely in both space and time and may be indicative of specific types of storms and/or specific stages in convective development. Indeed, we find that NBEs are more prevalent in, and perhaps indicative of, the strongest convection. However, even the strongest convection (as inferred by radar) does not always produce NBEs. We compare these results to past studies of NBEs which were based in Florida. We also briefly discuss the implications of these results for satellite-based VHF lightning detection. Copyright 2008 by the American Geophysical Union.