A numerical study on the effect of ice nucleation on thundercloud lightning behavior

A three-dimensional (3-D) cumulus model with electrification and lightning process is used to investigate the differences in electrification and lightning process between different ice crystal nucleation schemes. Three ice crystal nucleation schemes are adopted in this study, which are the original empirical formula YS scheme and DE scheme and LP scheme associated with aerosols. The present study indicates that the micro-process and electrification and lightning process of thunderstorm are influenced by different ice crystals nucleation schemes. Simulation results show that:(1) ice crystals appear in high temperature (>-13.8℃) region in the two new schemes associated with aerosols, the vertical distribution of ice crystals in DE scheme and LP scheme is greater than that in the YS scheme throughout the thundercloud development process; (2) ice crystals in high temperature region with charges in DE scheme and LP scheme show an obvious polarity reversal phenomenon, which leads to differences in the charge structure among the three schemes. The charge structure is tripolar in DE and LP scheme across the development time of thunderstorm, while it is dipolar in the YS scheme during the entire lifespan of the thunderstorm. The charge distribution area and the number of charges in DE and LP scheme are greater than in the YS scheme; (3) the thundercloud discharge behavior in different schemes is discrepant. Negative cloud-to-ground lightning is not generated in YS scheme because of the dipolar charge structure, whereas the lower positive charges in DE and LP scheme increase negative cloud-to-ground lightning and negative leader segments appear in the lower levels; the intra-cloud flash frequency and the transmission of positive and negative leader segments significantly increase in DE and LP scheme because the magnitude of charge in DE scheme and LP scheme are greater than that in YS scheme.