Numerical Modeling Studies of Storm Electrification and Lightning

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This project investigates the electrification and lightning production in mesoscale convective systems (MCSs), using a sophisticated three-dimensional numerical model with advanced microphysical, electrical and lightning parameterizations. The primary motivation for this numerical study is to gain physical understanding of the processes affecting electrification and lighting production from field observations of electrical storms by testing hypotheses derived from those observations. The principal investigators utilize improvements made to the model to study the time evolution of the horizontal/vertical charge structure of MCSs, those factors contributing to, and the lighting resulting from that structure. The ability to simulate the full life cycle of systems generates more robust correlations between lighting and storm properties. Specifically, they are comparing the relative contributions of local (stratiform region) charge separation processes versus advection of charge from the convective region, and testing the hypothesis that an inductive melting-fragmentation charge scheme is responsible for the near 273 K charge layers found in stratiform regions. Furthermore, they are studying the impact of the storm's evolution on its lighting production, focusing on the impact of merger or proximity of cells in the convective region, and ways in which the evolving charge structures in convective and stratiform regions interact to produce the often-observed cloud-to-ground lightning dipole (negative flashes near the convective region, positive from the stratiform region) and long horizontal flashes between the regions.The broader impacts of this work are its contribution to our understanding of the processes leading to storm electrification and lightning production, and high potential to resolve the current debate in the literature of the origins of charge in mesoscale convective systems. It aids in the interpretation of existing field observations, and will guide the design of future experiments. Two graduate students are funded under this work, and aspects of the research will find its way into a graduate course on atmospheric electricity at the University of Oklahoma, thus impacting many more students.