Simulation of cloud-to-ground lightning strikes to structures based on an improved stochastic lightning model

摘要

An improved stochastic method for computer simulation of lightning leaders is developed based on the results from optical observation data. The development and attachment process of downward negative cloud-to-ground lightning in the near-ground area is simulated. The distribution of lightning strike points influenced by tall structures is statistically analyzed. The results show that when downward negative leaders initiate at 1500 m height over a structure, the relative strike frequency for the structure increases at a decreasing rate as the structure height increases. The strike frequency for a 600 m tall structure is approximately 3.6 times that for a 100 m tall structure. Additionally, the structure may attract some lightning to hit itself and shift nearby ground strike points toward the structure. For taller structures, the deviation effect is more apparent. It is stipulated in this study that if the ground strike density in the vicinity of the structure is no more than 5% of the average density, then the structure has a sufficient protective effect on this area. The data indicate that there is a positive correlation between the protection distance and the height of the structure. The protection distances of structures of 100-600 m in height are 200 m, 280 m, 350 m, 400 m, 450 m, and 480 m approximatively, which show a declining rate of increase.