Research on Electrical Properties of Severe Thunderstorms in the Great Plains

Abstract

In 1978 we began a coordinated effort to study the electrical behavior of large and severe thunderstorms that form over the Great Plains of the central United States. Methods of approach include the study of characteristics of individual phenomena and storm case studies. Our goal is to understand the interrelationships between electrical phenomena and the dynamics and precipitation of storms. Evidence that interrelationships do exist can be seen in the results to date. In one squall-line storm we have studied. 44% of all observed lightning flashes wore cloud-to-ground (CG); the total flashing rate averaged 12 min⁻¹ and coarsely followed the changes in Doppler-derived maximum updraft speed. Most of the intracloud (IC) discharge processes in a supercell severe storm were located predominately around the region of the intense updraft of the mesocyclone and near large gradients in reflectivity and horizontal velocity. Both 10 cm and 23 cm wavelength radars have been used to detect lightning radar echoes. The lightning echoes from the 10 cm radar generally had peak signals 10–25 dB greater than the largest precipitation echo in the storm, and they usually were observed where precipitation reflectivities were less than maximum. Comparison of lightning echoes and electric field changes shows that abrupt increases in radar reflectivity often are associated with return strokes and K-type field changes. CG flashes that lower positive charge to earth have been observed to emanate from the wall cloud, high on the main storm tower, and well out in the downwind anvil of severe storms. The percentage of CG flashes that lower positive charge is apparently small.