Impact of ice multiplication on the cloud electrification of a cold-season thunderstorm: a numerical case study.

Ice microphysics controls cloud electrification in thunderstorms, and the various secondary ice production (SIP) processes are vital in generating high ice concentration. However, the role of SIP in cold-season thunderstorms is not well understood. In this study, the impacts of SIP on the electrification in a thunderstorm occurred in late November is investigated using model simulations. The parameterizations of three SIP processes are implemented in the model, including the rime-splintering, ice-ice collisional breakup, and shattering of freezing drops. In addition, a noninductive and an inductive charging parametrization, as well as a bulk discharging model are coupled with the spectral bin microphysics scheme. The results show the simulated storm intensity and temporal variation of flash rate are improved after SIP parametrizations are implemented in the model. Among the three SIP processes, the rime-splintering and shattering of freezing drops have stronger impacts on the storm than the ice-ice collisional breakup. The graupel and snow concentration are enhanced while their sizes are suppressed due to the SIP. The changes in the ice microphysics result in substantial changes in the charge structure. The total charge density changes from an inverted tripole structure to a dipole structure (tripole structure at some locations) after SIP is considered in the model, mainly due to the enhanced collision between graupel and ice, and riming at temperatures warmer than -20 °C. These changes lead to an enhancement of vertical electric field, especially in the mature stage, which explains the improved modelling of flash rate. The results highlight that the cold-season cloud electrification is very sensitive to the SIP. [ABSTRACT FROM AUTHOR]