Different precipitation mechanisms produce heavy rain with and without lightning in Japan

During summer,disturbed weather brings frequent bouts of heavy rain to japan in two types of cloud systems,one with high lightning activity and the other with low lightning frequency. to find the basis for this difference,data from three baiu and two non-baiu japanese heavy rain events in 2008–2009 were compared with videosonde data from various cloud systems across east and southeast asia. this analysis suggests that heavy rain is produced by two different precipitation mechanisms: by graupel growth in high-electrical-activity clouds and by frozen drop growth in low-electrical-activity clouds. high electrification is achieved only in graupel-growing clouds,where numerous ice crystals also grow and the riming electrification process is active. © 2015,meteorological society of japan.