Anomalously Low Negative Cloud-to-Ground Lightning Flash Rates in Intense Convective Storms Observed during STERAO-A

Abstract

Concurrent measurements from the CSU-CHILL multiparameter Doppler radar, the Office National d'Etudes et de Recherches Ae rospatiales VHF lightning interferometer, and the National Lightning Detection Network, obtained during phase A of the Stratosphere-Troposphere Experiments: Radiation, Aerosols, Ozone (STERAO-A) field project, provided a unique dataset with which to study the relationships between convective storm microphysics and associated lightning. Two storms have been examined in detail in this study: 10 and 12 July 1996. Both storms were long lived, existing in some form for over 4 h apiece, and produced very low cloud-to-ground (CG) lightning flash rates, in particular negative CG flash rates (generally 1 min 1 and often no CG flashes for periods ranging from 10 to almost 30 min), during all or a portion of their lifetimes while simultaneously producing relatively high intracloud (IC) flash rates (30 min 1 at peak). For both storms, radar reflectivity intensity and the production of hail were anticorrelated with the production of significant negative cloud-toground lightning. These observations are shown to be consistent with an elevated charge hypothesis and suggest a possible way of correlating updraft speed, hail, and storm severity to CG and IC flash rates.