Relationships between cloud-to-ground flashes and ice-phase hydrometeors in a tropical hailstorm

Abstract

Based on observed lightning locations and S-band polarimetric Doppler radar data, a hailstorm that occurred on Hainan Island was analyzed in detail. The hailstorm initially developed offshore to the southwest of Hainan Island. After the hailstorm made landfall, hail fell on the surface of Hainan Island for 43 min. An analysis revealed that the activity of cloud-to-ground flashes (CGs) peaked in the early mature stage of the hailstorm, followed by four intermittent CG flash active periods. The relationships between the CG flash frequency and the ice-phase hydrometeors retrieved from polarimetric parameters were compared, revealing that the CG flash activity was most closely related to graupel and snow particles in the cloud, whose correlation coefficients reached 0.8 and 0.76, respectively. In combination with the evolutionary features of the hailstorm, we found four independent periods of CG flash activity corresponding to different stages of the hailstorm: the merging of cloud bodies, the landfall of the convective body, the period of hailfall, and the period of orographic uplift. During these periods, the vertical distributions and concentrations of graupel and snow particles were distinct. During the hailfall period, the most significant vertical rate of change in radar echo intensities larger than 40 dBZ was located in the region of 0–10 °C, and this rate of change was the largest of the whole hailstorm.