How does the melting impact charge separation in squall line? A bin microphysics simulation study

A new electrification and discharge model was developed based on a two‐moment bin microphysical scheme coupled with the Weather Research and Forecasting (WRF) model. Based on the electrical model, the role of the noninductive charging mechanism associated with the melting processes of both snow and graupel (rimed particles) in the charge structure formation in the stratiform region of an organized convective system was examined. Our results showed that the snow melting charging mechanism forms a substantial positive charge layer near and below 0°C isotherm in the stratiform region of a squall line. It was also found that the graupel melting charging process mostly enhanced the positive charge layer in the convective region with little impact in the stratiform region. The in situ charging of noninductive collisional and melting processes and the charge transportation from the convective core all contribute to the charge structure formation in the stratiform region of a squall line.