Reply on RC2

Abstract. The determination of whether a cloud will evolve into a thunderstorm is beneficial for understanding thunderstorm formation and important for ensuring the safety of society. However, a clear understanding of the microphysics in clouds for the occurrence of lightning activity has not been attained. Vast field observations and laboratory experiments indicate that graupel, which is rimed ice, is a vital hydrometeor for lightning generation, and is the foundation of riming electrification. In this study, polarimetric radar and lightning observations are used to compare the ice microphysics associated with graupel between 57 isolated thunderstorms and 39 isolated non-thunderstorms, and the differences in radar parameters are quantified. Our results for the occurrence of lightning activity in clouds showed the following results: 1) the maximum difference in graupel volume on the −10 °C isotherm height between thunderstorms and non-thunderstorms reached approximately 7.6 km3; 2) the graupel particles approached spherical shapes with a mean ZDR value of 0.3 dB, which likely indicated heavily rimed graupel was present; and 3) 98.2 % of thunderstorms were equipped with the ZDR column, and the mean depth was ~2.5 km. Our study deepens our understanding of lighting physics and thunderstorm formation.