Characteristics of Lightning Discharges to Wind Turbines and Weather Conditions at Upper Air in Winter in Japan

The authors have observed lightning strokes occurring in a coastal area of the Sea of Japan, where is the most active area of winter lightning in the world. Catastrophic accidents have been frequent at wind farms in those areas due to winter lightning. We have analyzed the characteristics of lightning strokes hitting wind turbines and the relationship between those and temperatures at the upper-air layer. We used the datasets observed by the Japanese Lightning Detection Network (JLDN) for this analysis. We showed the seasonal differences in the characteristics of lightning strokes hitting the wind turbines. Our studies showed that lightning strokes were more concentrated near the wind turbines in winter than in summer. This is one of the characteristics of winter lightning due to discharges initialized upward from tall structures. We also showed the relationship between the ratios of lightning strokes that occurred in the vicinity of the wind turbine and the temperatures at the 700 hPa level and the altitude of −10°C isotherm altitude. We discussed how to define the occurrence conditions of winter lightning using the relationship shown above.