Investigating the Relative Contribution of Charge Deposition in Organizing Charge within a Thunderstorm

Many processes contribute to the hydrometeor charge budget within a thunderstorm. These include advection, hydrometeor differential sedimentation, turbulent mixing and diffusion, microphysical separation, and the attachment of ionic charge deposited by the lightning channel. Previous observational studies used balloon soundings of thunderstorm electric fields to quantify charge deposited by the lightning channel and concluded that charge deposition complicates the charge structure of a thunderstorm. The Kinematic Texture and Lightning (KTaL) campaign at Texas Tech University is designed to study aspects of the charge redistribution budget, with a particular focus on quantifying turbulence, but as with all observation campaigns quantification of the complete budget is challenging. Therefore, it is helpful to use other means of quantifying the relative contributions of charge deposition hydrometeor motions to the overall budget.

The NSSL version of the Collaborative Model for Multiscale Atmospheric Simulation (COMMAS) contains microphysical charging and branched lightning parameterizations. The model produces fairly realistic representations of intra-cloud (IC) and cloud-to-ground (CG) flashes that concur with previous observational analyses. This branched lightning scheme calculates advection, sedimentation, and turbulent mixing of charged hydrometeors in addition to the charge density deposited post-flash on each hydrometeor category. To assess the relative contribution of charge deposition, current work includes simulating storms using soundings from the KTaL field campaign and validating simulations with Lightning Mapping Array (LMA) data to evaluate the overall contribution from each contributor to the charge density tendency equation. Additionally, a frontogenesis approach of electric potential has been taken to analyze regions of strengthening electric field within the simulated storm in order to predict the most likely regions for lightning initiation.