摘要
该文分析了2007年广州从化人工引雷试验中,6月30日一次空中触发负极性闪电的光学和电学观测资料,结果表明:此次空中触发闪电的上行正先导和下行负先导分别出现了多个分叉。上行正先导早于下行负先导4.93 ms始发,上行正先导初始阶段的二维平均速度为104m/s量级,后增加到105m/s量级。下行负先导经历了3次分叉后分为4个分支接地,其中有两个接地分支一直持续发光到闪电放电结束,观测到下行负先导的二维平均速度为1.69×105m/s。小回击之后上行正先导也出现了多个分支,高速摄像和宽带干涉仪对这些分支的观测结果基本一致。小回击之后,初始长连续电流过程的持续时间为178.6 ms。
Field experiments on artificially rocket-triggered lightning are conducted in summer of 2007 in Conghua, Guangdong Province by Lightning Physics and Protection Engineering Laboratory of Chinese Academy of Meteorological Sciences. The luminosity characteristics of lighting are captured simultaneously by a Redlake MotionPro HS-4 high-speed camera at 5000 frames per second （fps） 630 m away. Field mill, magnetic loop antenna, broadband interferometers, slow antenna and fast antenna are installed at the experiment site. The time constants of slow and fast antenna are 6 s and 2 ms respectively, and the bandwidth of broadband interferometers to locate the lightning is from 25 MHz to 290 MHz. One lightning is successfully triggered at 13：58.33 30 June 2007. The top of the wire is 335 m height and the bottom of it is 170 m height at that time. The records of the electric field on the land surface show that it is a negative altitudetriggered lightning. No return stroke is observed in luminosity, and the initial continue current process of this flash is 178.6 ms. Bi-directional leader process occurs before mini return stroke and upward stepped leader branches of this altitude-triggered lightning occur after that. The upward positive leader appears 4.93 ms earlier before the downward negative leader. The upward stepped leader propagates at an average speed of the order of 104 m/s in its initial stage, and then becomes 10s m/s in magnitude. After the downward negative leader appears, the upward positive leader channel becomes brighter than before. The downward negative leader has 3 bifurcation points and produces 4 different ground contacts, and two branches connects to ground persisted during the initial continue current process. The average speed of the down- ward stepped leader is 1.69 × 10^5 m/s. After mini return stroke, the upward positive leader above the wire channel propagates along several different branch channels into the cloud, and the average speed of it is 1.05× 10^5 m/s. In this experiment, the inducing charge provides the charge of the leader to spread, and the environmental electric field may play a decisive role to the multiple branches and multiple ground contacts of this altitude-triggered lightning.
出处
《应用气象学报》
CSCD
北大核心
2010年第1期95-100,共6页
Journal of Applied Meteorological Science
基金
国家自然科学基金项目(40605004
40875003)
公益性行业(气象)科研专项(GYHY(QX)200706022)
中国气象科学研究院基本科研业务费专项资助
关键词
空中触发闪电
双向先导
多分叉
多接地点
altitude-triggered lightning
bi-directional leader
multiple branches
multiple ground contacts
