【摘要】 通过对 1998年 8月 2 2日空中引发雷电先导过程的光、电观测资料的综合分析发现 ,在空中引发雷电的先导系统中存在三个先导过程。①向下发展的负先导在起始阶段呈小阶梯特征 ,阶梯之间的时间间隔约为 2 0 μs ,阶梯的上升时间小于 1μs,随着负先导的下行发展 ,梯级增长。②金属导线上端向上发展的正先导在负先导接地之后 ,表现出明显的阶梯特性 ,阶梯之间的时间间隔平均为 15 μs。③从地面向上发展的连接正先导由多个振荡脉冲组成 ,脉冲之间的时间间隔约为 13μs,连接先导的发展也是梯级的。电场快变化中的高频分量随着距离的增加衰减很快。最强的发光是由向下的负先导接地时形成的小回击产生的 ,强光只集中在空气离化而形成的放电通道部分 ,光强则随着高度的增加很快衰减 ,其传播速度约为 2 .1× 10 8m·s-1。在小回击发生之前 ,向下发展的负先导在接地之前有较强的发光 ,而金属导线上端向上发展的正先导没有明显的发光。在小回击发生之后 ,金属导线上端向上正先导的发光强度被增强 ,其向上的传播速度约为 2 .4× 10 6m·s-1。金属导线部分在小回击发生之后约 2 2 0μs逐渐开始熔化发出强光 ,并向上发展而与前面向上发展的正先导的发光相并合 ,其传播速度约为 1× 10 6m·s-1更多还原

【Abstract】 The optical and electrical data of triggered lightning in altitude on 22 August 1998 were analyzed. The results indicated that there were three leader processes in triggered lightning in altitude. A negative leader propagated downward from bottom end of wire in a discontinuous pulses pattern with intervals of about 20 μs and rise time of less 1 μs. A positive leader starting from the top end of wire showed a pulses pattern with the intervals of 15 μs after the negative leader reached the ground. Meanwhile, a positive leader was initiated from the ground and propagated upward in discontinuous pulses pattern with intervals of 13 μs when the negative leader approachedthe ground. Following this was a minireturn stroke which emit intense light only in the channel section between ground and bottom end of wire and had an upward speed of 2.1×10 8 m·s\+\{-1\}. The negative leader emit more intense light than the positive leader initiated from the top end of wire before minireturn stroke. The light emit by the positive leader initiated from the top end of wire was intensified and propagated upward in speed of 2.4×10 6 m·s\+\{-1\} after minireturn stroke. The wire was melted after 220 μs of minireturn stroke and had intense light which propagated upward in speed of 1.0×10 4 m·s\+\{-1\}更多还原