Lightning Activity in the Outer Rainbands of Typhoon DOKSURI (2023) and Its Relationship with Heavy Rainfall Microphysical

For the extreme heavy rainfall process of Typhoon Doksuri in 2023, a joint observation was conducted using three-dimensional lightning location network, dual polarization weather radar, FY-4A satellite TBB data, ground automatic stations, typhoon data，wind profile radar and ERA5 reanalysis data. Based on these multi-source data, this study investigated the convective precipitation features and the characteristics of lightning activity within the rainbands of Duksuri, and analyzed in detail the relationship between lightning activity and microphysical characteristics of thunderstorm cloud with different organizational structures in the Mesoscale Convective System(MCS) within the outer rainbands. The results show that during Duksuri’s landfall, both typhoon eyewall, the inner and outer rainbands produced convective precipitation with high efficiency. The convective precipitation in the outer rainbands was more significant in terms of intensity, impact range, and duration compared to the eyewall and inner rainbands. Lightning activity had a lower frequency in the eyewall and inner rainbands, but a highest frequency in the outer rainbands. Lightning was mainly distributed in the MCS in the outer rainbands, with negative cloud-to-ground flash being the main type. During the mature stage of MCS in the outer rainbands, there were thunderstorm clouds with different convective structures, which produced significant differences in lightning frequency. Lightning frequency was lower in the coastal areas of northeastern Fujian, while it was much higer in the coastal areas of central Fujian. Using the vertical structure inversion results of dual polarization weather radar with multiple parameters, it was found that the strong thunderstorm clouds in the heavy rainfall-weak lightning-activity region had a low convective center of gravity as the main echo, and was composed of high-concentration liquid raindrops. Therefore, the heavy rainfall was caused by a strong warm rain process. In contrast, the main convective center of the strong echo in the heavy rainfall-strong lightning-activity region was higher, and the content and size of ice-phase particles on the melting layer were also higher. Below 0 ℃ layer, there were active high-concentration large rain droplets, as well as mixed-phase particles such as hail and ice crystals, which leads to the occurrence of intense lightning activity. Below 0 ℃ layer, the deep and strong updraft in the mixed phase zone in the heavy rainfall-strong lightning-activity region is conducive to the generation of lightning, while the liquid phase particles dominate in the heavy rainfall-weak lightning-activity region, and the strong updraft layer is shallow.