Electrical Structure of Storm Systems that Produce Positive Cloud-to-Ground Lightning

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9807179BeasleyCloud-to-ground lightning flashes that lower positive (CG+), rather than negative, charge to ground have been the object of intense study because they are anomalous, particularly energetic, and have unusual current characteristics. Past research has shown that CG+ tend to occur in specific convective storm situations and also are connected in some way with the recently discovered "sprites", which are discharges from thunderstorm tops to the upper atmosphere. The Principal Investigators will participate in a large cooperative project to study the electrical, dynamical and microphysical characteristics of storms that produce CG+. This project, knows as the Mesoscale Convective System Electrification and Polarimetric Radar Study (MEaPRS), will bring to bear a variety of instruments to observe cloud microphysics, x-rays, electric field and field changes, lightning strike locations, radar reflectivity, winds, and polarimetric radar variables.This research will employ balloon-borne measurements and numerical cloud modeling to study the distribution of the electric field and charge in mesoscale convective systems (MCSs) and in isolated severe storms that produce positive cloud-to-ground lightning. The occurrence of positive ground flashes in these types of storms has been documented, but the electrical structures of the storms are not yet well understood.Vertical profiles of electric field and charge density have been acquired in a few MCSs, which typically produce scattered positive ground flashes in the stratiform region. There have been enough profiles to develop a conceptual model of the stormÆs electrical structure that has been composited from several cases. Never have the electrical characteristics of all the major regions of a single MCS been sampled. A goal of the proposed research is to obtain observations of electric field and particle charge to evaluate the relative contribution of each of these charging processes to observed charge distributions. Soundings will be made in all of the major regions of individual MCSs to determine the distribution and temporal development of charge, especially in the stratiform region. ***