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In this investigation, time series consisting of electric field waveforms of 15 positive return strokes and 10 negative return strokes were analyzed. The data came from a summer thunderstorm in March in a range of about 200 km around São José dos Campos, São Paulo. The electric field recording system consisted of a flat plate antenna with a decay time constant of 260 μs and a sample rate of 800,000 samples per second. The bandwidth observed was up to 100 kHz and the recording system was synchronized with GPS time and located at São José dos Campos. Wavelet analysis of the electric field waveforms was done in order to investigate the behavior of the return stroke spectrum in time. The return stroke was suggested to be divided into two portions: initial stage and overshoot (for far return stroke) and initial stage and ramp (for close return stroke). The return stroke power spectrum was observed to be distributed in a frequency range with the peak value also distributed in a fraction of this range. Power peaks for ramps are stronger than power peaks for initial stage and overshoot. Finally, it was observed how powerful the wavelet is in the analysis of lightning. 相似文献
3.
Radio frequency observations of cloud-to-ground lightning (CG) were made in 1999 in Guangdong Province with the broadband
lightning interferometer. In this paper, radiation source locations and electric field waveforms are analyzed for different
types of breakdown events, including the preliminary breakdown of in-cloud activities, the stepped leaders of initial strokes
to ground and activities during and following return strokes. It is shown that the structure and development of lightning
discharges and associated breakdown processes can be reconstructed by using this new type of lightning radiation source location
system. The detectable radiation of lightning was primarily produced by the negative breakdown process. The channel was concentrated
with few branches during the preliminary breakdown stage of CG lightning flashes. The radiation sources appeared generally
at the tip of the channel. During the late period of the stepped leader, the radiation sources were dispersed with branches
extended away from the main channel. The radiation sources were in a certain length segment of the channel and the altitude
of the segment descended along with the propagation of the leader to the ground. During the preliminary breakdown and the
stepped leader of initial strokes to the ground, a sequence of fast negative streamers were observed to start continually
from or farther away the lightning-initiated region and propagate along the developed leader channel, which may supply negative
charge that assisted the leader’s development. The progression speed of fast negative streamers was about ten times faster
than the average speed of lightning channel. 相似文献
4.
《Journal of Atmospheric and Solar》2007,69(13):1569-1586
During the northern hemisphere winter of 2005–2006, transient luminous events (TLEs) known as ‘sprites’ and ‘elves’ were imaged over thunderstorm cells in the eastern Mediterranean. Simultaneously, extremely low frequency (ELF) data (ELF: 3–3000 Hz) were recorded at two observation stations in Israel and Hungary in order to qualify and quantify parameters of the parent lightning discharge associated with the transient optical emissions in the upper atmosphere. In this study, we found that for 87% (Israel) and 77% (Hungary) of optically observed TLEs an intense ELF transient event was recorded. These stations are located some 500 and 2100 km, respectively, from the region of the TLEs. All ELF transients that were associated with TLEs were caused by lightning discharges with positive polarity. Calculation of the charge moment change showed values between 600 and 2800 C km with a peak around 1000 C km. Additionally, the time delay between the +CG and ensuing sprite was 76±34 ms and it was displaced up to 50 km from its parent CG.One of our objectives in the present study was to characterize, based on the ELF radiation from lightning, the electromagnetic (EM) waveforms of the lightning discharges which generate TLEs in the time and frequency domains, and to compare them with other lightning discharges occurring in the same thunderstorm cell at approximately the same time, but which did not produce TLEs. The survey for a typical EM waveform showed no unique ELF signature for lightning discharges associated with either sprites or elves. 相似文献
5.
《Journal of Atmospheric and Solar》2007,69(12):1397-1406
As the electromagnetic fields propagate over finitely conducting ground, selective attenuation of the high frequencies takes place. As a result, the signatures of broad-band electromagnetic radiation fields generated by lightning flashes change as they propagate over such ground. In addition to being a function of the electrical parameters of the ground over which the electromagnetic fields propagate, these propagation effects depend on the height of their source above ground level. This makes the propagation effects on radiation fields from cloud flashes differ from those on the radiation fields generated by return strokes in ground flashes. In this paper the propagation effects on radiation field pulses of cloud flashes are illustrated and it is shown that these effects are not as severe as those of return strokes in ground flashes. 相似文献
6.
V. A. Rakov 《Surveys in Geophysics》2013,34(6):731-753
Both cloud-to-ground and cloud lightning discharges involve a number of processes that produce electromagnetic field signatures in different regions of the spectrum. Salient characteristics of measured wideband electric and magnetic fields generated by various lightning processes at distances ranging from tens to a few hundreds of kilometers (when at least the initial part of the signal is essentially radiation while being not influenced by ionospheric reflections) are reviewed. An overview of the various lightning locating techniques, including magnetic direction finding, time-of-arrival technique, and interferometry, is given. Lightning location on global scale, when radio-frequency electromagnetic signals are dominated by ionospheric reflections, is also considered. Lightning locating system performance characteristics, including flash and stroke detection efficiencies, percentage of misclassified events, location accuracy, and peak current estimation errors, are discussed. Both cloud and cloud-to-ground flashes are considered. Representative examples of modern lightning locating systems are reviewed. Besides general characterization of each system, the available information on its performance characteristics is given with emphasis on those based on formal ground-truth studies published in the peer-reviewed literature. 相似文献
7.
本文利用已有的随机放电参数化方案,结合四次探空资料,进行了12.5 m的高分辨率二维雷暴云数值模拟实验,得到了各种雷暴云电荷结构下的地闪个例,并就地闪击地点与空间电荷、电位分布之间的相互关系进行了分析.结果表明:(1)由空间电荷唯一确定的电位分布决定了先导的传播最大趋势,而闪电传播的随机性所带来的地闪击地点的不确定范围被限制在3 km之内,利用动态聚类法迭代得出的三个击地点位置之间的差为1 km左右.(2)负地闪的初始点与击地点的位置差主要分布在0~6 km范围内,且93%的负地闪分布在0~4 km范围内,正地闪的分布相对较广,0~3 km范围内占48%,3~6 km范围内占34%,6~10 km范围内占18%.(3)正、负地闪主要产生于离地面最近的一对电荷堆之间,其起始高度越高,初始点与击地点位置差分布越广;另外,产生于三级性雷暴云电荷结构下的正地闪,其起始于上部的主正电荷堆与中部主负电荷堆之间,由于下行正先导会绕过底部的次正电荷堆,因此其击地点与初始点的距离基本在6 km以上. 相似文献
8.
本文在已有的三维雷暴云起、放电模式中加入了一种经典的气溶胶活化参数化方案,结合一次长春雷暴个例,进行了雷暴云起放电数值模拟试验.研究显示气溶胶浓度改变对雷暴云微物理、起电及放电过程都有重要影响.结果表明:(1)污染型雷暴云中气溶胶浓度增加时,云滴数目增多,上升风速加强;云中冰晶与霰粒子数浓度增加但尺度减小;(2)相对于清洁型雷暴云,污染型雷暴云非感应起电过程弱,感应起电过程强,起电持续时间长;(3)污染型雷暴云中首次放电时间延迟,闪电持续发生的时间长,总闪电频次增加,正地闪频次增加明显. 相似文献
9.
利用闪电作为辐射源来探测电离层D层是近年来国外学者研究的热点.本文基于江淮流域六站同步闪电观测站网,实现了一种利用闪电双极性窄脉冲事件（Narrow Bipolar Events,NBE）来探测电离层D层等效高度的方法.基于此方法,对两次分别发生在日出和日落阶段的雷暴分析结果显示,上述两个阶段D层反射高度变化特征呈现显著的不对称性：日出期间D层反射高度随时间线性降低速率为5.9 km/h;而日落期间D层反射高度随时间线性递增速率为8.6 km/h.综合日间太阳耀斑期间D层反射高度剧烈波动的观测事实,与日出、日落期间D层特征变化,结果表明太阳辐射电离中性大气分子的电子生成机制在日间D层电子密度变化中占主导地位.本文结果展现了利用NBE事件监测电离层D层变化特征的可行性,这一方法与基于地闪回击波形的D层探测方法结合在一起,有望把现有具有闪电事件定位和电磁波波形记录能力的闪电观测站网扩展为实时对电离层D层时空变化监测的网络. 相似文献
10.
利用闪电放电辐射源三维时空分布测量,分析了山东低海拔地区一次多单体雷暴过程的电荷结构演变以及与回波强度的关系.结果表明对流云区电荷结构是典型的上正下负电偶极结构,且随着雷暴发展正负电荷层强度增大,高度抬升.负电荷区处在40 dBz以上的强回波区域中,正电荷层处在约40 dBz区域中.层状云区也有类似结构,只是强度弱,高度低.观测到的四层电荷结构是出现在对流区消散阶段,此时,由于云体不同部位的不同消散程度,电荷结构发生断裂,云体前部正负电荷区下沉,云体中部正负电荷区高度变化不大,但负电荷区域变薄,呈现出四层电荷结构.从本例结果说明,雷暴优势起电机制通常能形成电偶极或三极性结构,多极结构可能不是起电形成.本文还分析了一次负地闪传输过程,和宏观电荷结构很好吻合,说明利用三维定位系统观测,可以较好地描述雷暴宏观电荷结构. 相似文献
11.
L. P. Babich 《Geomagnetism and Aeronomy》2007,47(5):664-670
The results of the experiments, during which we revealed that the flux of neutrons in the atmosphere increases in correlation with electromagnetic pulses of lightning discharges, have been analyzed. The mechanisms of charged particle acceleration and nuclear reactions that can be responsible for neutron generation have been analyzed. It has been indicated that the probability of nuclear synthesis reactions in a lightning channel, which is traditionally considered as the source of neutrons in a thunderstorm atmosphere, is extremely low. The generation of neutrons in thunderstorm electric fields is related to photonuclear reactions in gigantic upward atmospheric discharges caused by relativistic runaway electron bremsstrahlung. 相似文献
12.
K. A. Nicoll 《Surveys in Geophysics》2012,33(5):991-1057
Measurements of the electrical characteristics of the atmosphere above the surface have been made for over 200?years, from a variety of different platforms, including kites, balloons, rockets and aircraft. From these measurements, a great deal of information about the electrical characteristics of the atmosphere has been gained, assisting our understanding of the global atmospheric electric circuit, thunderstorm electrification and lightning generation mechanisms, discovery of transient luminous events above thunderstorms and many other electrical phenomena. This paper surveys the history of atmospheric electrical measurements aloft, from the earliest manned balloon ascents to current day observations with free balloons and aircraft. Measurements of atmospheric electrical parameters in a range of meteorological conditions are described, including clear air conditions, polluted conditions, non-thunderstorm clouds, and thunderstorm clouds, spanning a range of atmospheric conditions, from fair weather to the most electrically active. 相似文献
13.
利用闪电宽带干涉仪系统对闪电的观测表明，地闪和云闪的云内闪电通道都存在双向发展的特征. 闪电在云中负电荷区域初始激发以后，在通道两端发生向不同方向同时发展的击穿过程. 这两种击穿过程均产生较强的辐射，且辐射频谱特征十分相似，表明云内闪电通道两端发生的击穿过程可能均为负击穿过程. 相应电场变化表明闪电通道双向发展期间伴随着负电荷的向上转移. 这一观测事实与Kasemir早期提出的闪电通道双向发展的概念有一定的差异. 相似文献
14.
《中国科学:地球科学(英文版)》2017,(10)
In recent years, locating total lightning at the VLF/LF band has become one of the most important directions in lightning detection. The Low-frequency E-field Detection Array(LFEDA) consisting of nine fast antennas was developed by the Chinese Academy of Meteorological Sciences in Guangzhou between 2014 and 2015. This paper documents the composition of the LFEDA and a lightning-locating algorithm that applies to the low-frequency electric field radiated by lightning pulse discharge events(LPDEs). Theoretical simulation and objective assessment of the accuracy and detection efficiency of LFEDA have been done using Monte Carlo simulation and artificial triggered lightning experiment, respectively. The former results show that having a station in the network with a comparatively long baseline improves both the horizontal location accuracy in the direction perpendicular to the baseline and the vertical location accuracy along the baseline. The latter results show that detection efficiencies for triggered lightning flashes and return strokes are 100% and 95%, respectively. The average planar location error for return strokes of triggered lightning flashes is 102 m. By locating LPDEs in thunderstorms, we find that LPDEs are consistent with convective regions as indicated by strong reflectivity columns, and present a reasonable distribution in the vertical direction.In addition, the LFEDA can reveal an image of lightning development through mapping the channels of lightning. Based on three-dimensional locations, the vertical propagation speed of the preliminary breakdown and the changing trend of the leader's speed in an intra-cloud and a cloud-to-ground flash are investigated. The research results show that the LFEDA has the capability for three-dimensional location of lightning, which provides a new technique for researching lightning development characteristics and thunderstorm electricity. 相似文献
15.
ZHAGN Yijun DONG Wansheng ZHAO Yang ZHANG Guangshu Zhang Hongfa CHEN Chengpin ZHANG Tong 《中国科学D辑(英文版)》2004,47(Z1)
The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges.A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection. 相似文献
16.
Yijun Zhagn Wansheng Dong Yang Zhao Guangshu Zhang Hongfa Zhang Chengpin Chen Tong Zhang 《中国科学D辑(英文版)》2004,47(1):108-114
The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges. A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection. 相似文献
17.
H. R. Pruppacher 《Pure and Applied Geophysics》1967,68(1):186-195
Summary The results of a recent investigation on the free growth rate and the growth forms of ice in supercooled water and aqueous solutions are presented. The results are used to discuss the structure of frozen drops, the structure of hailstones, the mechanisms which are responsible for the glaciation of atmospheric clouds and the mechanisms which cause cloud electrification. It was found that the presence of dissolved salts and dust particles in cloud drops favor the formation of spongy and polycristalline ice, that it is unlikely for frozen cloud drops to develop into hexagonal shaped ice single-crystals, and that it is also unlikely that in atmospheric clouds freezing drops shatter and splinter. The latter result casts serious doubts on the splintering mechanism to contribute to thunderstorm electrification and to promote glaciation of clouds.This work was supported by the National Science Foundation under Grant No. GP 2922. 相似文献
18.
Vernon Cooray Mahbubur Rahman Vladimir Rakov 《Journal of Atmospheric and Solar》2009,71(17-18):1877-1889
Different approaches are used in estimating the global production of NOx by lightning flashes, including field measurements carried out during thunderstorm conditions, theoretical studies combining the physics and chemistry of the electrical discharges, and measurements of NOx yield in laboratory sparks with subsequent extrapolation to lightning. In the latter procedure, laboratory data are extrapolated to lightning using the energy as the scaling quantity. Further, in these studies only the return strokes are considered assuming that contributions from other processes such as leaders, continuing currents, M components, and K processes are negligible. In this paper, we argue that the use of energy as the scaling quantity and omission of all lightning processes other than return strokes are not justified. First, a theory which can be used to evaluate the NOx production by electrical discharges, if the current flowing in the discharge is known, is presented. The results obtained from theory are compared with the available experimental data and a reasonable agreement is found. Numerical experiments suggest that the NOx production efficiency of electrical discharges depends not only on the energy dissipated in the discharge, but also on the shape of current waveform. Thus, the current signature, can influence extrapolation of laboratory data to lightning flashes. Second, an estimation of the NOx yield per lightning flash is made by treating the lightning flash as a composite event consisting of several discharge processes. We show that the NOx production takes place mainly in slow discharge processes such as leaders, M components, and continuing currents, with return strokes contributing only a small fraction of the total NOx. The results also show that cloud flashes are as efficient as ground flashes in NOx generation. In estimating the global NOx production by lightning flashes the most influencing parameter is the length of the lightning discharge channel inside the cloud. For the total length of channels inside the cloud of a typical ground flash of about 45 km, we estimate that the global annual production of NOx is about 4 Tg(N). 相似文献
19.
Spatiotemporal characteristics of positive cloud-to-ground lightning discharges and bidirectional leader of the lightning 总被引：4，自引：0，他引：4
Krehbiel Paul 《中国科学D辑(英文版)》2006,49(2):212-224
The negative CG lightning discharges neutralizing negative charges in cloud usually dominate for most of thunderstorms. However, a lot of positive CG light-ning discharges often occur in the disappearing stage of thunderstorms, in the stratiform region of mesoscale convective systems and some supercells producing hail and tornado. Because the positive CG lightning discharges produce larger current of the return stroke and neutralize more charges due to the continuing currents with longer las… 相似文献
20.
T. Neubert M. Rycroft T. Farges E. Blanc O. Chanrion E. Arnone A. Odzimek N. Arnold C.-F. Enell E. Turunen T. Bösinger Á. Mika C. Haldoupis R. J. Steiner O. van der Velde S. Soula P. Berg F. Boberg P. Thejll B. Christiansen M. Ignaccolo M. Füllekrug P. T. Verronen J. Montanya N. Crosby 《Surveys in Geophysics》2008,29(2):71-137
The paper reviews recent advances in studies of electric discharges in the stratosphere and mesosphere above thunderstorms,
and their effects on the atmosphere. The primary focus is on the sprite discharge occurring in the mesosphere, which is the
most commonly observed high altitude discharge by imaging cameras from the ground, but effects on the upper atmosphere by
electromagnetic radiation from lightning are also considered. During the past few years, co-ordinated observations over Southern
Europe have been made of a wide range of parameters related to sprites and their causative thunderstorms. Observations have
been complemented by the modelling of processes ranging from the electric discharge to perturbations of trace gas concentrations
in the upper atmosphere. Observations point to significant energy deposition by sprites in the neutral atmosphere as observed
by infrasound waves detected at up to 1000 km distance, whereas elves and lightning have been shown significantly to affect
ionization and heating of the lower ionosphere/mesosphere. Studies of the thunderstorm systems powering high altitude discharges
show the important role of intracloud (IC) lightning in sprite generation as seen by the first simultaneous observations of
IC activity, sprite activity and broadband, electromagnetic radiation in the VLF range. Simulations of sprite ignition suggest
that, under certain conditions, energetic electrons in the runaway regime are generated in streamer discharges. Such electrons
may be the source of X- and Gamma-rays observed in lightning, thunderstorms and the so-called Terrestrial Gamma-ray Flashes
(TGFs) observed from space over thunderstorm regions. Model estimates of sprite perturbations to the global atmospheric electric
circuit, trace gas concentrations and atmospheric dynamics suggest significant local perturbations, and possibly significant
meso-scale effects, but negligible global effects. 相似文献