Revealing the mechanism of lightning generation is beneficial to understand meteorological process and evaluate atmospheric chemistry, further, it is important for ensuring space vehicle safety and large crowds safe at venues like sporting events, concerts, etc. However, by far, clearly understanding how the first lightning flashes (FLFs) occur in thunderstorms is still difficult. Vast field observations and laboratory experiments believe that graupel, the rimed ice, is the vital hydrometeor for lightning generation, which is the foundation of riming electrification. In addition, latent heat released by riming is the dynamical foundation for severe storms formation. But graupel is universally present in convective clouds, some storms are still no lightning. Our study picked a better scheme (comparing the ice microphysics between 57 thunderstorms and 39 non-thunderstorms instead of studying the evolution variation within the same thunderstorm) to study the microphysical characteristics for the FLF occurrence within isolated warm-season based on polarimetric radar and lightning observations over South China. Results indicate that more graupel volume and/or more riming could produce the FLF more probable, in addition, deeper Z_DR column is associated with the FLF occurrence. That would be helpful for deepening the understanding on lighting physics.

thunderstorm; lightning; riming; cloud microphysics