CAJ | 학술논문

三维雷电观测系统LMA(Lightning Mapping Array)是最近发展起来的基于GPS时钟同步的闪电VHF辐射源到达时间差(TOA)定位技术,能以很高的时间分辨率(50 ns)和空间定位精度(50-100 m)展现闪电放电发展过程的三维时空分布,揭示雷暴中电荷结构及其与放电过程的关系.文中利用三维雷电VHF辐射源观测资料分析了负地闪预击穿过程的时空分布特征,讨论了云下部正电荷区对负地闪发生的影响,其结果表明在首次回击之前存在长时间预击穿过程的负地闪中,预击穿过程是云中部负电荷区与下部正电荷区之间的一种云内放电过程,闪电起始于云中部负电荷区,然后向下发展传输,进入正电荷区后闪电通道在云下部正电荷区水平发展,其放电特征与反极性云闪放电一致,云内放电过程最后阶段的K型击穿激发了地闪的梯级先导,梯级先导穿过云下部正电荷区向下发展传输.云下部正电荷的存在是导致负地闪首次回击之前存在长时间云内预击穿过程的主要原因.
삼유뇌전관측계통LMA(Lightning Mapping Array)시최근발전기래적기우GPS시종동보적섬전VHF복사원도체시간차(TOA)정위기술,능이흔고적시간분변솔(50 ns)화공간정위정도(50-100 m)전현섬전방전발전과정적삼유시공분포,게시뇌폭중전하결구급기여방전과정적관계.문중이용삼유뇌전VHF복사원관측자료분석료부지섬예격천과정적시공분포특정,토론료운하부정전하구대부지섬발생적영향,기결과표명재수차회격지전존재장시간예격천과정적부지섬중,예격천과정시운중부부전하구여하부정전하구지간적일충운내방전과정,섬전기시우운중부부전하구,연후향하발전전수,진입정전하구후섬전통도재운하부정전하구수평발전,기방전특정여반겁성운섬방전일치,운내방전과정최후계단적K형격천격발료지섬적제급선도,제급선도천과운하부정전하구향하발전전수.운하부정전하적존재시도치부지섬수차회격지전존재장시간운내예격천과정적주요원인.
A new lightning locating technology, called Lightning Mapping Array (LMA), has been developed. The system takes the advantage of GPS technology to measure the times of arrival (TOA) of lightning impulsive VHF radiation events at each remote location. The temporal and 3-D spatial development processes of lightning are described by measurements of the system with high time resolution (50 ns) and space precision (50-100 m). The charge structures in thunderstorms and the relationship between the charge structure and lightning discharge processes are revealed. The temporal and spatial characteristics of preliminary breakdown process in negative cloud-to-ground(CG) lightning discharges are analyzed based on the data of lightning VHF radiation events. The effect of the positive charge region in the lower part of thunderstorms on the occurrence of negative CG lightning discharge is discussed. The results indicate that the preliminary breakdown process with longer lasting time of negative CG lightning discharges is an intracloud discharge process between the negative and positive charge regions located in the lower and middle parts of thunderstorms respectively. It initiated from the negative charge region in the middle part and propagated downward. After entered the positive charge region in the lower part, the lightning channel developed horizontally. The characteristics of preliminary breakdown process are consistent with that of inverted intracloud lightning discharges. The stepped leaders were initiated by the K type breakdown which occurred in the last stage of the preliminary breakdown process and penetrated downward through the positive charge region. The existence of positive charge region in the lower part of thunderstorms is the reason why there is a preliminary breakdown process with longer lasting time in thunderstorms before the first return stroke of negative CG lightning discharges take place.