Further Analysis and Modeling Studies of Severe Thunderstorm Electrification and Precipitation Study (STEPS) Cases

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This project continues the work initiated earlier on analysis and modeling of storms observed on the STEPS program (Severe Thunderstorm Electrification and Precipitation Study) conducted in Kansas in the early summer of 2000. It includes the analysis of cloud electrical and microphysical data collected by the storm-penetrating T-28 aircraft and modeling the production of charge and precipitation with a three-dimensional numerical cloud model. The research is carried out in collaboration with other STEPS investigators, who will provide data including polarimetric radar measurements to identify precipitation type, dual-Doppler radar measurements to define the kinematic structure of thunderstorms, balloon-borne electrical field measurements, and three-dimensional maps of lightning strokes measured by a VHF lightning mapper. Attention will focus on the storms of 11 June and 29 June 2000. A major objective is to explain why some storms produce predominantly positive cloud-to-ground lightning discharges while others produce negative discharges. A synthesis of the electrical, microphysical, and storm-structure data will lead to a better understanding of the mechanism of lightning formation in thunderstorms and the relations between electrical properties of storms and the precipitation they produce.