Characteristics of winter lightning current on Japan Sea Coast

Long-term observation of winter lightning has been conducted on the Japan Sea Coast since 1978. From various kinds of observations, the results of lightning current measurement by an automatic lightning current recording system are reported. It is shown that winter lightning current has wide variations in its waveform, but the frequency distribution of the front duration, the tail duration, and the front steepness can be approximated by a logarithmic normal distribution. Positive polarity lightning current tends to have much longer front and tail duration than negative lightning current. The ratio of the positive to the negative polarity is one to two in winter lightning, which is much higher than that of summer lightning. The cumulative frequency distribution of the winter lightning current peak agrees with that of the summer lightning current. The fractional distribution was proposed for winter lightning protection design