Numerical Modeling Studies of Storm Electrification and Lightning

该项目研究了中尺度对流系统（mcs）中的电气化和闪电产生，使用了一个复杂的三维数值模型，具有先进的微物理、电和闪电参数化。这项数值研究的主要动机是通过测试从这些观测得出的假设，从电风暴的现场观测中获得对影响电气化和照明生产过程的物理理解。主要研究人员利用对模型的改进来研究MCSs的水平/垂直电荷结构的时间演变，这些因素的影响，以及由该结构产生的照明。模拟系统整个生命周期的能力在光照和风暴特性之间产生了更强的相关性。具体来说，他们比较了局部（层状区域）电荷分离过程与对流区域电荷平流的相对贡献，并测试了感应熔化-碎片电荷方案是在层状区域发现的近273 K电荷层的原因。此外，他们正在研究风暴演变对其照明产生的影响，重点是对流区域细胞合并或接近的影响，以及对流和层状区域不断变化的电荷结构相互作用产生经常观测到的云对地闪电偶极子（对流区域附近的负闪，层状区域的正闪）和区域之间的长水平闪的方式。这项工作的更广泛的影响是它有助于我们理解导致风暴电气化和闪电产生的过程，并有很大的潜力解决目前文献中关于中尺度对流系统电荷起源的争论。它有助于解释现有的实地观测结果，并将指导未来实验的设计。两名研究生得到了这项工作的资助，这项研究的一些方面将在俄克拉荷马大学的大气电学研究生课程中找到方法，从而影响更多的学生。

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.