Lightning activity and its associations with cloud structures in a rainstorm dominated by warm precipitation

Abstract Lightning activity and its associations with cloud structures during a rainstorm dominated by warm cloud precipitation were studied in Guangdong, China on May 7, 2017, using three-dimensional lightning location and polarimetric radar data. The overall convection and lightning activities of the rainstorm were weak. The rainstorm generally showed a typical tripolar charge structure with the main negative charge core located between the −15 and − 8 °C environmental isotherms in the first 4 h. The height of the charge regions clearly decreased after this period, with the main negative charge core being below the −8 °C isotherm. Lightning discharges were more concentrated in areas featuring relatively weak convection and relatively low precipitation intensity. Most of the locations with lightning discharges were dominated by dry aggregated snow and weak updrafts and downdrafts. This investigation demonstrated that the lightning discharges were spatially separated from the area of origin of charging in this rainstorm. It is proposed that, with weak convection in the rainstorm, the charging rate was lower than the speed of charge transfer from the area of origin, causing a relatively low charge density and a low frequency of lightning in the area of origin of charging. Meanwhile, the aggregation of small charged particles in regions away from the area of origin of charging might be conducive to the formation of a relatively high charge density and therefore relatively frequent lightning flashes. This situation is different from a typical thunderstorm with strong convection.