Abstract:

Based on the nearly 11 a (2007-2017) cloud-to-ground lightning data monitored by the ADTD (Advanced TOA and Direction system) 2D lightning location system in Zhejiang province, the identification of thunderstorms and tracking their paths were realized using the density maximum fast search clustering and Kalman filtering algorithms.The spatial and temporal distribution characteristics of the process of large-scale thunderstorms were discussed.The results show that the above method can recognize and track all kinds of thunderstorms in Zhejiang province.261 tracks of thunderstorm processes are screened out, which show considerable annual and interannual variations.There is a good corresponding relationship between the number of the annual tracks and the frequency of annual lightning.The number of monthly tracks demonstrates a bimodal distribution, with peak values appearing in early spring and summer.The thunderstorms in spring generally move longer than those in other seasons.In the spatial distribution, the direction of 88.51% of thunderstorm tracks is from west to east, and more thunderstorms move toward the north.There is a difference in the monthly distribution of the number of thunderstorm tracks in each moving direction.The movement direction of thunderstorms in spring is more concentrated than those in summer.The dominant movement direction of summer thunderstorms is different.The moving speed of thunderstorms is about 50 km per hour.The thunderstorms moving from west to east and southwest to northeast are faster than in other directions.In terms of spatial distribution, there are two main mobile tracks.One is the area along the Jinqu basin, Shaoxing and Ningbo, the second is the area from Huzhou Jiaxing Plain to the north of Tianmu Mountain.From the perspective of topographic features, the tracks mainly occur in hilly areas, with relatively few plains and mountains, and the higher the terrain, the fewer paths.

Key words: Thunderstorm track, Cloud-to-ground lightning, Moving direction