Microphysical Structure and its Formation Process Relating to Cloud-to-Ground Lightning Characteristics of Thunderclouds

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Lightning activity is closely related to the hydrometeor types and those space-time distribution within thunderclouds. In this study, several thunderclouds which showed the distinctive characteristics of cloud-to-ground (CG) lightning were examined to reveal their microphysical structures and evolutions using the X-band polarimetric radars and the lightning location systems. A thundercloud with active .CG lightning started its lightning activity approximately 10 minutes after its occurrence. Polarimetric measurements indicate that a major hydrometeor within its strong echo region was graupel, while it was rain in a non-active thunderstorm. In a thunderstorm dominated +CG lightning, which is uncommon in warm season, it is considered that the positively charged wet graupel in the middle level of the cloud contributed to the generation of the +CG lightnings.