15:45 〜 16:00
[MIS13-02] 2018年8月26日に観測された青天の霹靂の放電経路の特徴
キーワード：雷、青天の霹靂
A bolt from the blue (BFB) is a phenomenon where lightning progress from the side of a thundercloud to outside the cloud, leading to lightning strikes in distant locations. There is limited research on BFB domestically and internationally, and the mechanism of lightning progression from the side of thunderclouds to outside the cloud is not well understood. It is important to clarify the characteristics of lightning progression inside and outside the cloud. We demonstrated that a single thundercloud that occurred in the northern Kanto region on August 26, 2018, was accompanied by 18 BFBs (Kudo and Sakurai, 2023). In this study, we examined the characteristics of lightning progression inside and outside the cloud for four BFBs that could be matched by video and photographs.
The horizontal discharge distances within the rain area (the intensity of precipitation near the ground > 1mm/h) of the four BFBs ranged from 1.6 km to 3.7 km, and the horizontal discharge distances outside the rain area ranged from 2.0 km to 4.9 km. The average horizontal discharge distances inside and outside the rain area were 2.9 km and 3.5 km, respectively, with the outside rain area discharge distance being slightly longer.
For three of the four BFBs, the starting altitude of discharge was around 6.5-7 km, with the starting altitude outside the rain area being 5-6 km. We confirmed the altitude change associated with the progression of discharge inside the cloud for these three BFBs, with two progressing downward (towards the ground) and one progressing almost horizontally within the cloud. However, another BFB started discharging at an altitude of about 9 km, progressed slightly upward within the cloud after, and then discharged outside the cloud. The altitude of discharge outside the rain area was approximately 9.5 km. In the future, we plan to investigate the correspondence between the distribution of precipitation particles inside the cloud and the discharge paths.
The horizontal discharge distances within the rain area (the intensity of precipitation near the ground > 1mm/h) of the four BFBs ranged from 1.6 km to 3.7 km, and the horizontal discharge distances outside the rain area ranged from 2.0 km to 4.9 km. The average horizontal discharge distances inside and outside the rain area were 2.9 km and 3.5 km, respectively, with the outside rain area discharge distance being slightly longer.
For three of the four BFBs, the starting altitude of discharge was around 6.5-7 km, with the starting altitude outside the rain area being 5-6 km. We confirmed the altitude change associated with the progression of discharge inside the cloud for these three BFBs, with two progressing downward (towards the ground) and one progressing almost horizontally within the cloud. However, another BFB started discharging at an altitude of about 9 km, progressed slightly upward within the cloud after, and then discharged outside the cloud. The altitude of discharge outside the rain area was approximately 9.5 km. In the future, we plan to investigate the correspondence between the distribution of precipitation particles inside the cloud and the discharge paths.