Measurement of Lightning Current at Wind Turbine Near Coast of Sea of Japan in Winter

The authors have carried out measurement of the current waveforms associated with lightning discharges to wind turbines near the coast of the Sea of Japan in Tohoku. In this paper, measured waveforms in winter from 2013 to 2018 are investigated and the charge transfer of lightning flash initiated by upward propagating leaders is studied. The charge transfer associated with bipolar lightning is higher than that associated with unipolar lightning. The lightning charge transfer of the typical winter atmospheric pressure pattern thunderstorms (TWPs) with relatively low -10 °C isotherm altitude is less than that of OTT (other thunderstorms than the TWP) at Nikaho and in Tohoku. In Hokuriku, another winter lightning area, the charge transfer of the lightning flash is almost the same regardless of the above-mentioned two types of the thunderstorms as well as the -10 °C isotherm altitude. As the result, it is pointed out that the charge transfer is dependent on the -10 °C isotherm altitude and types of thunderstorms, and that characteristics of winter lightning depend on the region. It is commonly found that the charge transfer exceeding 300 C occurs when the altitude of -10 °C isotherm is between 1000 and 2500 m above the sea level.