A Numerical Study of Aerosol Effects on the Electrification and Flash Rate of Thunderstorms

A two-dimensional cumulus model coupled with an aerosol module is used to simulate a case of tropical convection in Nanjing. Numerical simulations at a resolution of 250 m are performed to investigate the effect of aerosol concentration on the electrification and lightning flash rate in the thunderstorm clouds. In this aerosol module, the distribution of aerosol particles is fitted by superimposing three log-normal distribution functions, and the activation of aerosol particles to form cloud droplets is considered. The results show that: (1) The charge structure in the thundercloud remains a triple charge structure as the aerosol concentration increases. (2) When the aerosol concentration is changed from 50 to 1000 cm^-3, a stronger formation of cloud droplets, graupel and ice crystals results in an increasing charge separation and lightning flash rate. (3) In the range of 1000-3000 cm^-3, the decrease in ice crystals caused by vapor competition leads to a reduction in upper positive charge, while the enhancement of graupel and cloud droplets results in the contribution of inductive charge to the middle negative charge region and lower positive charge region increasing with greater aerosol concentration. The flash rate shows a slight change. (4) At very high aerosol concentrations (above 3000 cm^-3), the magnitude of the charge and lightning flash rate, which remains steady in the thundercloud, is insensitive to aerosol concentration.