资源环境科技发展态势分析平台

A total of 254 flashes observed in 14 mesoscale convective systems in Chongqing, China, during the summers of 2014-2015 was used to investigate the characteristics of lightning flashes in stratiform regions (stratiform lightning flashes). The data were analyzed and combined with data from an S-band Doppler radar system. The results show that the reflectivity characteristics of stratiform lightning flashes are different from those of convective lightning flashes. More than 90% of the stratiform lightning flashes had close spatial relationship with the areas in which bright bands were identified in the vertical direction. The reflectivity at the first detected veryhighfrequency sources of most stratiform lightning flashes decreased with increasing core reflectivity within the lightning extension area. Further investigations showed that only a small proportion (<= 10%) of the stratiform lightning flashes were directly initiated by the charge corresponding to the reflectivity cores. It suggests that the reflectivity cores (mostly bright bands) and stratiform lightning flashes are close in space, but different in causality. Some in situ electrifications in stratiform regions, such as nonriming noninductive electrification and melting electrification, are inferred to cause this relationship. The stratiform lightning flashes initiated from lower altitudes tended to have a lower maximum reflectivity within their lightning areas, but a higher maximum reflectivity in the vertical direction of their initiation locations than flashes initiated at higher altitudes.