Numerical Simulation on the Effect of Ice Nuclei on the Electrification Process of Thunderstorms

This work is conducted based on an existing two-dimensional convective cloud model to investigate the role of ice nuclei in dynamic, microphysical, electrification, and charge structure in thunderstorm clouds by changing the concentration of ice nuclei. The results show that thunderstorm clouds develop ahead of time as ice nuclei increase and both updraft and downdraft velocities decrease. A high concentration of ice nuclei enhances the heterogeneous nucleation process. In the high-temperature region, a large number of ice crystals form while the homogeneous nucleation process is inhibited. Therefore, the overall content of ice crystals decreases, resulting in a decrease in graupel content in the low-temperature region and a decrease in graupel size in the high-temperature region. Therefore, the positive non-inductive electrification rate decreases while the negative non-inductive electrification rate increases. The time for the polarity of charge carried by high-temperature ice crystals to change from negative to positive is advanced as the liquid water content gradually decreases with increasing ice nuclei concentration. The extreme value of the inductive electrification rate gradually decreases during the process of inductive electrification due to the decrease in graupel particle size and the rapid consumption of cloud droplets. Because the ice crystals are preferentially generated in the high-temperature region and are negatively charged, the space charge structure of thunderstorm clouds with different ice nuclei concentrations presents a negative dipole charge structure at the initial stage of thunderstorm cloud development. With an increase in ice nuclei concentration, the space charge structure changes from three polarities to a complex four-order structure during the thunderstorm’s growing period. In the dissipation stage of a thunderstorm cloud, different cases show dipole charge structures, and the charge density decreases with the increased concentration of ice nuclei.