Lightning activity in the outer rainbands of typhoon Doksuri （2023） and its relationship with the microphysical structure of heavy rainfall

Base on observations of three-dimensional lightning location network, dual polarization weather radars, ground automatic stations and wind profile radars as well as FY-4A satellite TBB data, typhoon data, and ERA5 reanalysis data, convective precipitation features and characteristics of lightning activities within the rainbands of typhoon Duksuri that occurred in 2023 are analyzed. The relationship between lightning activities and microphysical characteristics of thunderstorm clouds with different organizational structures in the Mesoscale Convective System (MCS) within the outer rainband are analyzed in detail by using statistical and diagnostic methods. The results show that during Duksuri's landfall, both typhoon eyewall and the inner and outer rainbands produced convective precipitation with high efficiency. The convective precipitation in the outer rainband was more significant in terms of intensity, impact range and duration compared to that in the eyewall and inner rainband. Lightning activities had a lower frequency in the eyewall and inner rainband and the highest frequency was found in the outer rainband. Lightnings were mainly distributed in the MCS in the outer rainband, with negative cloud-to-ground flash being the main type. During the mature stage of MCS in the outer rainband, 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 higher in the coastal areas of central Fujian. Based on vertical structure inversion results of dual polarization weather radar and multiple parameters, it is found that the strong thunderstorm clouds in the heavy rainfall-inactive lightning area had a low convective center of the main echo, which 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-active lightning area 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 raindrops and ice phase particles, which led to the occurrence of intense lightning activity. Below 0℃ layer, there was deep and strong updraft in the mixed phase zone in the heavy rainfall-active lightning area, while the heavy rainfall-inactive lightning area was dominated by liquid phase particles, and the strong updraft layer was shallow. The above results provide a reference basis for the characteristics of lightning activities in the rain bands outside typhoons and their relationship with the microphysical structure of heavy rainfall.