Influence of tilting effect on charge structure and lightning flash density in two different convective environments

Abstract

The influence of the tilting effect on charge density and lightning flash density was investigated using idealized Weather Research and Forecasting explicit charging/discharge module (WRF-ELEC) simulations for two thunderclouds. No shear (NS) and with shear (WS) simulations were conducted based on different values of wind velocity components in input sounding. Results from the NS and WS simulations show that the tilting effect extended the lifetime of the simulated convective clouds in both case studies, while leading to higher maximum vertical velocity only for the environment with intense convection. The ice and graupel in the cloud cell appear almost simultaneously in both the NS and WS simulations for the two case studies, but larger values are obtained for the WS simulations. It is noted that the increase of convection intensity postpones the larger values to the mature stage. The tilting effect results in an increase of total non-inductive charging, especially in a severe thundercloud. Moreover, the tilting effect does not lead to the same results for the polarity and intensity of charge density in the two studied cases. In the real case study, a dipolar charge structure was seen for both NS and WS simulations, but the intensity of charge density decreased with regard to the tilting effect. In contrast, the intensity of the charge increased with the tilting effect and resulted in tripolarity in the idealized case with a high value of convective available potential energy. Finally, considering the tilting effect leads to an increase of the number of lightning occurrences in the two case studies.