Characteristic of Lightning Channel in the Thundercloud from Thunder

我们测量了23个雷声记录在沼津山附近。1992年5月在富士山，1990年以来在金泽附近的Tubata和Shishiku高地冬季。(1)雷电信号分为三种类型。第一种类型是最大的声音在开始时在0.5秒内到达，之后逐渐变弱。第二种是先有弱音，然后逐渐变强，再逐渐减弱。第三种类型是第一种或第二种类型重复。(2)冬雷的平均持续时间为20秒。第三类雷是在冬季闪电中观测到的，持续时间几乎都在30秒以上。(3)功率谱的平均主频为140 Hz，距离主通道小于5 km的近雷为150 Hz，距离大于5 km的远雷为67 Hz。从雷电数据采样周期与传声器配置的关系出发，明确了声源定位的空间分辨率。当四个传声器等间距地位于原点和直角坐标轴上时，对任意方向声的分辨率小于200 <3>Δ/D，Δ为采样误差，由冬季雷电重建了闪电通道，得到以下结果：（1）不同点的闪电偶尔出现第三类雷电; (2)闪电通道的中心在1.5 ~ 2km高度范围内，水平通道的长度大于15 km。

We measured 23 thunder records at Numazu near Mt. Fuji on May in 1992, and at Tubata and Shishiku Heights near Kanazawa in winter since 1990. (1) Thunder signatures are classified into three types. The first type is that the largest sound arrives within 0.5 sec at the outset and after that becomes gradually weaker. The second type is that weak sound comes first and becomes stronger step by step and after that gradually weakens. The third type is that the first or the second type repeats. (2) The mean duration of thunder is 20 sec in winter thunder. The thunder of the third type is observed in winter lightning and has almost long duration more than 30 sec. (3) The dominant frequency of power spectrum is 140 Hz on the average, the nearby thunder less than 5km to main channel is 150Hz, on the other hand the thunder of long distance more than 5km is 67Hz.It is shown that the channels of long duration thunder are reconstructed by determining the time window length from zero-crossing number, and the channels of a multistroke lightning are reconstructed from the dominant thunder signals.The spatial resolution of sound source location is made clear from the relation sampling period of thunder data and microphone configuration. When four microphones are located at the origin and on right angled axes in equal separation of D meaters, the resolution is less than 2ROO<3>DELTAS/D for any directional sounds, where DELTAS is sampling error.The lightning channels are reconstructed from the winter thunder and the following results are derived : (1) Lightning of simultanous strokes to different points presents occasionally the third type of thunder. (2) The center of lightning channels is in the range 1.5km and 2km altitude and the horizontal channel is longer than 15km in horizontal extent.