人工触发闪电上行正先导起始阶段放电特征
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摘要
上行正先导是上行负地闪始发及下行负地闪连接中的重要放电过程,但由于观测困难,所以其始发机制仍不是十分清楚。为此,基于2014—2015年广东野外雷电综合观测试验中获取的人工触发闪电通道底部电流、近距离电场等同步观测资料,分析了触发闪电上行正先导(upward positive leader,UPL)整个起始阶段的放电特征。结果表明:UPL起始阶段通道底部电流波形表现为不连续的脉冲形式,以单个或者成组的形式出现,其中UPL连续传输之前的电流脉冲峰值、10%~90%上升时间、波形持续时间、半峰值宽度、转移电荷量、脉冲时间间隔的几何平均值(GM)分别是28 A、0.33μs、2.3μs、0.73μs、27μC、25μs,而连续传输开始时刻的电流脉冲相应的波形参数几何平均值分别为32 A、0.54μs、3.5μs、0.93μs、46μC、24μs,2者相比,连续传输开始时电流脉冲具有更大的转移电荷量。同时,UPL对应的近距离电场波形呈现出明显的梯级变化,每个电场脉冲与通道底部电流脉冲具有良好的时间对应关系,这表明触发闪电UPL在起始阶段表现出了梯级的发展特征。
Upward positive leader(UPL) is the key discharge during the initiation of upward negative lightning and the connection of downward negative lightning. However, it is not enough to understand the physical mechanism during the inception stage of UPL. Based on the synchronous data of channel-base current and close-distance electric field generated by triggered lightning detected in Guangdong comprehensive observation experiment for lightning discharge, the discharge characteristics of UPL during the initial stage of triggered lightning are analyzed. The waveform of channel-base current for upward positive leader exhibits discontinuous pulses, which occur separately or in groups. Statistical analysis shows that the geometric mean(GM) values of current peak, 10%~90% rise time, duration, half peak width, transferred charge, and pulse interval for the pulses generated before the appearance of continuously upward leader are 28 A, 0.33 μs, 2.3 μs, 0.73 μs, 27 μC, and 25 μs, respectively. The GM values of the corresponding parameters for the pulses generated during the initiation of continuously upward leader are 32 A, 0.54 μs, 3.5 μs, 0.93 μs, 46 μC and 24 μs, respectively. Compared with the discharge process before continuous propagation of UPL, the discharge process during the inception of continuously upward leader transfers more charge. Also the waveforms of close-distance electric field show obviously step-change, and each pulse of electric field corresponds to the channel-base current pulses in time sequence, indicating that the cascade development has characteristics of upward positive leader during the initial stage of artificially triggered lightning.
Upward positive leader(UPL) is the key discharge during the initiation of upward negative lightning and the connection of downward negative lightning. However, it is not enough to understand the physical mechanism during the inception stage of UPL. Based on the synchronous data of channel-base current and close-distance electric field generated by triggered lightning detected in Guangdong comprehensive observation experiment for lightning discharge, the discharge characteristics of UPL during the initial stage of triggered lightning are analyzed. The waveform of channel-base current for upward positive leader exhibits discontinuous pulses, which occur separately or in groups. Statistical analysis shows that the geometric mean(GM) values of current peak, 10%~90% rise time, duration, half peak width, transferred charge, and pulse interval for the pulses generated before the appearance of continuously upward leader are 28 A, 0.33 μs, 2.3 μs, 0.73 μs, 27 μC, and 25 μs, respectively. The GM values of the corresponding parameters for the pulses generated during the initiation of continuously upward leader are 32 A, 0.54 μs, 3.5 μs, 0.93 μs, 46 μC and 24 μs, respectively. Compared with the discharge process before continuous propagation of UPL, the discharge process during the inception of continuously upward leader transfers more charge. Also the waveforms of close-distance electric field show obviously step-change, and each pulse of electric field corresponds to the channel-base current pulses in time sequence, indicating that the cascade development has characteristics of upward positive leader during the initial stage of artificially triggered lightning.
引文
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[20]JIANG R B,QIE X S,WANG C,et al.Propagating features of upward positive leaders in the initial stage of rocket-triggered lightning[J].Atmospheric Research,2013,129-130(8):90-96.
[21]RAKOV V A,UMAN M A,RAIZER Y P.Lightning physics and effects[M].Cambridge,UK:Cambridge University Press,2006:208-209.
[22]ZHANG Y J,YANG S J,LU W T,et al.Experiments of artificially triggered lightning and its application in Conghua,Guangdong,China[J].Atmospheric Research,2014,135/136:330-343.
[23]ZHANG Y,ZHANG Y J,XIE M,et al.Characteristics and correlation of return stroke,M component and continuing current for triggered lightning[C]∥International Conference on Lightning Protection.Shanghai,China:[s.n.],2014:730-734.
[24]WILLETT J C,DAVIS D A,LAROCHE P.An experimental study of positive leaders initiating rocket-triggered lightning[J].Atmospheric Research,1999,51(3):189-219.
[25]LALANDE P,BONDIOU-CLERGERIE A,LAROCHE P,et al.Leader properties determined with triggered lightning techniques[J].Journal of Geophysical Research Atmospheres,1998,103(D12):14109-14115.
[26]UMAN M A.The lightning discharge[M].New York,USA:Dover Publications Inc,2001:314.
[27]NGIN T,UMAN M A,HILL J D,et al.Measurement and analysis of ground-level electric fields and wire-base current during the rocket-and-wire lightning triggering process[J].Journal of Geophysical Research,2013,118(17):10041-10055.
[2]曾嵘,周旋,王泽众,等.国际防雷研究进展及前沿述评[J].高电压技术,2015,41(1):1-13.ZENG Rong,ZHOU Xuan,WANG Zezhong,et al.Review of research advances and fronts on international lightning and protection[J].High Voltage Engineering,2015,41(1):1-13.
[3]张义军,孟青,Krehbiel P R,等.正地闪发展的时空结构特征与闪电双向先导[J].中国科学,2006,36(1):98-108.ZHANG Yijun,MENG Qing,KREHBIEL P R,et al.Temporal and spatial structure characteristics of positive ground flash development and lightning bidirectional leader[J].Science China Press,2006,36(1):98-108.
[4]QIE X S,ZHANG Y,ZHOU G,et al.Artificially triggered lightning and its characteristic discharge parameters in two severe thunderstorms[J].Science China:Earth Sciences,2007,50(8):1241-1250.
[5]张义军,吕伟涛,郑栋,等.负地闪先导-回击过程的光学观测和分析[J].高电压技术,2008,34(10):2022-2029.ZHANG Yijun,LüWeitao,ZHENG Dong,et al.Optical observations and analysis of leader-return stroke processes involvedin negative cloud-to-ground lightning flashes[J].High Voltage Engineering,2008,34(10):2022-2029.
[6]VLADISLAV M,RUHNKE L H.Common physical processes in natural and artificially triggered lightning[J].Journal of Geophysical Research Atmospheres,1993,981(D7):12913-12930.
[7]董万胜,刘欣生,张义军.一次人工触发闪电的宽带干涉仪观测[J].科学通报,2001,46(5):427-432.DONG Wansheng,LIU Xinsheng,ZHANG Yijun.The observation of a wide band interferometer for artificial triggered lightning[J].Chinese Science Bulletin,2001,46(5):427-432.
[8]姚尧,李健,李涵,等.基于山区雷电先导发展的改进电气几何模型仿真研究[J].高电压技术,2015,41(5):1550-1557.YAO Yao,LI Jian,LI Han,et al.Simulation research of improved electro-geometric model based on lightning leader development in mountainous terrain[J].High Voltage Engineering,2015,41(5):1550-1557.
[9]MCEACHRON K B.Lightning to the empire state building[J].Journal of the Franklin Institute,1939,227(2):149-217.
[10]YANG J,QIE X S,ZHANG Q,et al.Comparative analysis of the initial stage in two artificially-triggered lightning flashes[J].Atmospheric Research,2009,91(24):393-398.
[11]唐力,韩永霞,郝艳捧,等.高海拔地区特高压直流线路绝缘子的正极性先导发展法闪络判据[J].高电压技术,2016,42(6):1900-1906.TANG Li,HAN Yongxia,HAO Yanpeng,et al.Leader propagation model as positive flashover criterion of UHVDC line insulators at high altitude[J].High Voltage Engineering,2016,42(6):1900-1906.
[12]张义军,张阳,郑栋,等.2008—2014年广东人工触发闪电电流特征[J].高电压技术,2016,42(11):3404-3414.ZHANG Yijun,ZHANG Yang,ZHENG Dong,et al.Current characteristcs of triggered lightnings in guangdong from 2008 to 2014[J].High Voltage Engineering,2016,42(11):3404-3414.
[13]BIAGI C J,JORDAN D M,UMAN M A,et al.High-speed video observations of rocket-and-wire initiated lightning[J].Geophysical Research Letters,2009,36(36):66-78.
[14]BIAGI C J,UMAN M A,HILL J D,et al.Observations of the initial,upwardpropagating,positive leader steps in a rocket andwire triggered lightning discharge[J].Geophysical Research Letters,2011,38(24):87-94.
[15]BIAGI C J,UMAN M A,HILL J D,et al.Transient current pulses in rocket-extended wires used to trigger lightning[J].Journal of Geophysical Research:Atmospheres(1984—2012),2012,117(D7):7205-7221.
[16]LU W T,CHEN L W,ZHANG Y,et al.Characteristics of unconnected upward leaders initiated from tall structures observed in Guangzhou[J].Journal of Geophysical Research Atmospheres,2012,117(D19):161-169.
[17]JIANG R B,QIE X S,WANG Z,et al.Characteristics of lightning leader propagation and ground attachment[J].Journal of Geophysical Research Atmospheres,2015,120(23):90-96.
[18]LAROCHE P A,EYBERT-BERARD L B,BERLANDIS J P.Observations of preliminary discharges initiating flashes triggered by the rocket and wire technique[C]∥8th International Conference on Atmospheric Electricity.Uppsala,Swed:[s.n.],1988:353-359.
[19]王彩霞,郄秀书,蒋如斌,等.一次人工触发闪电上行正先导的传输特征[J].物理学报,2012,61(3):553-560.WANG Caixia,QIE Xiushu,JIANG Rubin,et al.Propagat-ing properties of an upward positive leader ina negative triggered lightning[J].ACTE Physica Sinica,2012,61(3):553-560.
[20]JIANG R B,QIE X S,WANG C,et al.Propagating features of upward positive leaders in the initial stage of rocket-triggered lightning[J].Atmospheric Research,2013,129-130(8):90-96.
[21]RAKOV V A,UMAN M A,RAIZER Y P.Lightning physics and effects[M].Cambridge,UK:Cambridge University Press,2006:208-209.
[22]ZHANG Y J,YANG S J,LU W T,et al.Experiments of artificially triggered lightning and its application in Conghua,Guangdong,China[J].Atmospheric Research,2014,135/136:330-343.
[23]ZHANG Y,ZHANG Y J,XIE M,et al.Characteristics and correlation of return stroke,M component and continuing current for triggered lightning[C]∥International Conference on Lightning Protection.Shanghai,China:[s.n.],2014:730-734.
[24]WILLETT J C,DAVIS D A,LAROCHE P.An experimental study of positive leaders initiating rocket-triggered lightning[J].Atmospheric Research,1999,51(3):189-219.
[25]LALANDE P,BONDIOU-CLERGERIE A,LAROCHE P,et al.Leader properties determined with triggered lightning techniques[J].Journal of Geophysical Research Atmospheres,1998,103(D12):14109-14115.
[26]UMAN M A.The lightning discharge[M].New York,USA:Dover Publications Inc,2001:314.
[27]NGIN T,UMAN M A,HILL J D,et al.Measurement and analysis of ground-level electric fields and wire-base current during the rocket-and-wire lightning triggering process[J].Journal of Geophysical Research,2013,118(17):10041-10055.