空中人工引发雷电的正负先导特征研究  

Study on the Characteristics of Positive and Negative Leader in Triggered Lightning in Altitude

作　　者：张义军[1] 刘欣生[1] 王才伟[1] 肖庆复[1] 张广庶[1] 董万胜[1] 周良才[2] 钟定珠[2] 樊灵孟[2] 陈明理[1] 王道洪[3] 渡边贞司[3] 

机构地区：[1]中国科学院寒区旱区环境与工程研究所,甘肃兰州730000 [2]广东省电力试验研究所,广东广州510600 [3]日本岐阜大学

出　　处：《高原气象》2001年第1期6-13,共8页Plateau Meteorology

基　　金：中科院重大项目!(KZ95 1 B1 40 5 );国家自然科学基金项目!(49975 0 0 3)的资助

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× 10The 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\}

关 键 词：空中引发雷电 先导传播 电场变化 负地闪 正地闪 

分 类 号：P427.32[天文地球—大气科学及气象学]