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1.
广州高建筑物雷电观测站光电同步观测系统于2017年6月16日记录到一次峰值电流达+141 kA的单回击正地闪触发两个并发上行闪电过程。利用高速摄像、普通摄像和电场变化数据分析了触发型上行闪电的始发特征和机理。结果表明:正地闪回击后约0.8 ms内,在距正地闪接地点约3.9 km的广州塔（高600 m）和4.1 km的东塔（高530 m）分别有上行闪电始发。正地闪回击过程中和大量正电荷以及之后可能有云内负先导朝高塔方向快速伸展造成塔顶局部区域的电场发生突变是两个上行闪电激发的原因。两个上行闪电在353 ms内发生7次回击,其中6次在广州塔上,仅1次在东塔上,且广州塔回击峰值电流平均值（-21.4 kA）约为东塔回击峰值电流（-7.3 kA）的3倍,表明广州塔上行闪电通道可能比东塔上行闪电通道伸展至分布范围更广、电荷量（或电荷密度）更大的负电荷区。两个上行闪电先导的二维速率变化范围为9.4×104~1.8×106 m·s-1,平均值为6.9×105 m·s-1。 相似文献
2.
Behnam Salimi Kamyar Mehranzamir Zulkurnain Abdul-Malek 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):133-137
Lightning is an electrical discharge during thunderstorms that can be either within clouds (Inter-Cloud), or between clouds and ground (Cloud-Ground). The Lightning characteristics and their statistical information are the foundation for the design of lightning protection system as well as for the calculation of lightning radiated fields. Nowadays, there are various techniques to detect lightning signals and to determine various parameters produced by a lightning flash. Each technique provides its own claimed performances. In this paper, the characteristics of captured broadband electric fields generated by cloud-to-ground lightning discharges in South of Malaysia are analyzed. A total of 130 cloud-to-ground lightning flashes from 3 separate thunderstorm events (each event lasts for about 4–5 hours) were examined. Statistical analyses of the following signal parameters were presented: preliminary breakdown pulse train time duration, time interval between preliminary breakdowns and return stroke, multiplicity of stroke, and percentages of single stroke only. The BIL model is also introduced to characterize the lightning signature patterns. Observations on the statistical analyses show that about 79% of lightning signals fit well with the BIL model. The maximum and minimum of preliminary breakdown time duration of the observed lightning signals are 84 ms and 560 us, respectively. The findings of the statistical results show that 7.6% of the flashes were single stroke flashes, and the maximum number of strokes recorded was 14 multiple strokes per flash. A preliminary breakdown signature in more than 95% of the flashes can be identified. 相似文献
3.
《大气与海洋》2013,51(3):177-194
Abstract Flash density and occurrence features for more than 23.5 million cloud‐to‐ground (CG) lightning flashes detected by the Canadian Lightning Detection Network (CLDN) from 1999 to 2008 are analyzed on 20 × 20 km equal area squares over Canada. This study was done to update an analysis performed in 2002 with just three years of data. Flashes were detected throughout the year, and distinct geographic differences in flash density and lightning occurrence were observed. The shape and locations of large scale patterns of lightning occurrence remained almost the same, although some details were different. Flash density maxima occurred at the same locations as found previously: the Swan Hills and Foothills of Alberta, southeastern Saskatchewan, southwestern Manitoba and southwestern Ontario. A region of greater lightning occurrence but relatively low flash density south of Nova Scotia occurred at the same location as reported previously. New areas of higher flash density occurred along the US border with northwestern Ontario and southern Quebec. These appear to be northward extensions of higher flash density seen in the previous study. The greatest average CG flash density was 2.8 flash km?2 y?1 in southwestern Ontario, where the greatest single‐year flash density (10.3 flash km?2 y?1) also occurred. Prominent flash density minima occurred east of the Continental Divide in Alberta and over the Niagara Escarpment in southern Ontario. Lightning activity is seen to be highly influenced by the length of the season, proximity to cold water bodies and elevation. The diurnal heating and cooling cycle exerted the main control over lightning occurrence over most land areas; however, storm translation and transient dynamic features complicated the time pattern of lightning production. A large portion of the southern Prairie Provinces experienced more than 50% of flashes between 22:30 and 10:30 local solar time. The duration of lightning over a 20 × 20 km square at most locations in Canada is 5–10 h y?1, although the duration exceeded 15 h y?1 over extreme southwestern Ontario. Lightning occurred on 15–30 days each year, on average, over most of the interior of the country. The greatest number of days with lightning in a single year was 47 in the Alberta foothills and 50 in southwestern Ontario. Beginning and ending dates of the lightning season show that the season length decreases from north to south; however, there are considerable east‐west differences between regions. The season is nearly year‐round in the Pacific coastal region, southern Nova Scotia, southern Newfoundland and offshore. 相似文献
4.
利用2007—2018年浙江省ADTD闪电定位资料,分析了该地区多回击地闪分布及相关参数特征。结果表明:浙江省多回击地闪占总地闪的26.74%,其中正闪以单回击地闪为主;正、负闪平均回击数分别为1.04次和1.65次,最大回击数分别为5次和21次。回击数和地闪数存在较为一致的年际变化,正、负多回击地闪日变化分别呈多峰和单峰分布。正、负多回击地闪电流强度算术平均值分别为72.06kA和-36.89kA,回击平均强度随回击数的增加而下降,约40%的地闪过程中至少有1次继后回击强度比首次回击强;首次回击和继后回击的强度分布呈对数正态分布,集中在15～45kA之间。正、负地闪回击间隔时间算术平均值分别为125.47ms和138.14ms,几何平均值分别为56.73ms和98.95ms,回击间隔时间呈对数正态分布,平均回击间隔时间随回击数的增大而减小。多回击地闪继后回击与首次回击之间距离与回击数呈准正态分布,集中在距离为1km范围内。 相似文献
5.
《大气与海洋》2013,51(4):443-454
Abstract Using data from Hydro‐Québec, a spatio‐temporal summary study of cloud‐to‐ground lightning in Quebec (45°‐53 °N; 81 °‐65° W) for the 1996–2005 period was performed on a sample of close to four million lightning strokes. The annual number of lightning strokes and the ratio of negative to positive lightning (76:24) do not differ significantly from one year to the next. Despite the fact that there was an average of 239 lightning days per year, the lightning strokes were concentrated over a period of a few days. Between 1996 and 2005, 50% of the total annual lightning was distributed over 11 days, 75% over 25 days, and 90% over 44 days. Overall, the peak in the average annual cycle occurs on 15 July. Between 1996 and 2002, the number of days with at least one positive lightning stroke remained higher than the number of days with at least one negative lightning stroke. This tendency reversed from 2003 until 2005. Most of the annual lightning occurred during June, July and August. The average minimum number of lightning strokes per hour occurred at approximately 14:00 utc, and the maximum number occurred at 21:00 UTC. The ratio of positive lightning to negative remained constant throughout the day. Both the density and the number of lightning days were mapped for the 10‐year period. The spatial distribution of lightning indicates a higher density in the southern and western parts of the study area with an average of 0.52 to 1.27 lightning strokes km?2 yr?1. The St. Lawrence Lowlands ecoregion receives the greatest number of lightning strokes annually (from 0.73 to 1.27 km?2 yr?1). The spatial distribution of the number of lightning days per year is approximately the same as that of the density. The same two gradient axes can be observed crossing from north to south and from east to west. The spatial distribution of the percentage of positive lightning strokes varies considerably in the area, ranging from 0 to 65% depending on the location. While the St. Lawrence Lowlands ecoregion has the highest density and highest number of lightning days, it also has the lowest number of positive strokes. Additional research must be done to establish a correlation between our results and environmental variables, such as topography and vegetation, as well as the spatial variations of lightning and instances of forest fire. 相似文献
6.
中国内陆高原地闪特征的统计分析 总被引：29，自引：3，他引：29
利用微秒级时间分辨率的宽带慢天线电场变化仪首次在中国内陆高原地区对雷暴过程中的正、负地闪特征进行了测量和系统分析 ,发现每次雷暴过程中正闪的比例有随总闪频数增大而减少的趋势 ,弱雷暴过程更有利于正地闪的产生。平均来讲 ,正地闪占闪电总数的 16 % ,介于美国夏季雷暴和日本冬季雷暴之间。负地闪闪击间隔的算术平均值和几何平均值分别为 6 4.3ms和 46 .6ms。 5 4%的负地闪有至少一次继后回击强度大于首次回击 ,而且有 2 0 %的继后回击其强度大于首次回击强度。继后回击强度与首次回击强度的比例几何平均值为 0 .46 ,算术平均值为 0 .70 ,平均回击数为 3.76 ,39.8%为单次回击地闪。正地闪的多次回击只占 13.0 % ,且闪击之间的时间间隔也较大 ,算术平均值为 91.7ms。 相似文献
7.
为了深入认识负地闪放电过程中光辐射信号的特性, 对广州高建筑物雷电观测站所获得的回击光脉冲波形进行了分析。对观测到的88例负地闪事件中的184次回击(包括60次下行闪电首次回击、58次下行闪电继后回击、66次上行闪电继后回击)的光脉冲特征进行了统计分析, 结果表明: 下行闪电首次回击光脉冲10%~90%上升时间T1的算术平均值/中值为32.5/31.4μs, 20%~80%上升时间T2的算术平均值/中值为22.6/22.4μs, 半峰宽度T3的算术平均值/中值为131.1/117.0μs。下行闪电继后回击光脉冲T1的算术平均值/中值为30.4/27.7μs, T2的算术平均值/中值为19.5/17.6μs, T3的算术平均值/中值为153.6/142.6μs。在21例下行多回击负地闪事件中, 光脉冲回击间隔时间在12.6~368.6 ms范围之间, 算术平均值为78.7 ms, 有14%闪电事件存在继后回击光脉冲峰值大于首次回击的情况。上行闪电继后回击光脉冲T1的算术平均值/中值为27.5/24.3μs, T2的算术平均值/中值为17.0/15.7μs, T3的算术平均值/中值为132.2/124.5μs。总体上, 下行闪电首次回击的光脉冲上升时间最长、下行闪电继后回击次之、上行闪电继后回击最小; 下行闪电继后回击脉冲半峰宽度比下行闪电首次回击及上行闪电继后回击的更大。 相似文献
8.
Abstract We have made a preliminary study of cloud‐to‐ground lightning over southern Ontario and the adjoining Great Lakes region. The lightning data set, using magnetic direction finding, is sufficiently accurate to study lightning climatology. Cloud‐to‐ground flash totals have been found for the three warm seasons 1989–91. A large variation in flash total, lightning‐day frequency and number of high flash density storms occurs over the area, with the maximum in southwestern Ontario. The area of the maximum also has a strong diurnal cycle and relatively few positive flashes. Several physical causes may contribute to this. Lake areas usually have slightly fewer flashes than nearby land areas and warm water usually has more flashes than cold water. The Great Lakes do produce more lightning than ocean areas. Convergence lines of lake breezes and other lake circulations can, however, be sites for storms with intense lightning. High surface temperature and moisture leads to an increase in lightning generation. Over land, upslope flow increases lightning‐producing storms and downslope flow decreases them. High flash density storms may be favoured by smooth rather than rough ground, and by open farmland rather than forest. On the other hand, there does not seem to be a clear urban effect increasing lightning in the Great Lakes 相似文献
9.
北京地区负地闪回击转移的电荷量 总被引：1，自引：1，他引：0
负地闪是闪电危害的主要来源,其对地转移电荷源特征和电荷量不仅对闪电放电机理的研究有重要意义,而且对雷电防护也具有重要的实际应用价值。为了研究具有典型城市下垫面环境的北京地区的闪电活动特征和放电强度,利用北京地区2011年两次雷暴过程的多站GPS(Global Position System)同步闪电地面电场变化定量观测资料,在考虑消除场地和环境因素对电场变化观测资料影响的基础上,基于蒙特卡洛数据处理方法和非线性最小二乘法拟合反演算法,定量研究了负地闪回击中和的电荷源位置和电荷量,并对回击特征与回击转移电荷源之间的关系进行了讨论,得到如下结果:(1)单次回击中和的电荷量为1.1~27.6 C,平均为8.6±5.2 C,不同序数回击转移电荷量的最小值基本不随回击序数的上升而变化,最大值和均值随回击序数的上升而减小;一次负地闪中和的总电荷量随着回击数的增加而增加。(2)负地闪回击数和回击时间间隔都呈对数正态分布,其中负地闪总数70.4%的多回击负地闪其回击间隔平均为99±95 ms,不同序数回击的时间间隔最小值随回击序数的上升基本不变,时间间隔最大值和均值随回击序数的上升而减小。(3)回击转移电荷量的均值随回击间隔的增加呈波动形式的逐渐上升;相邻回击转移电荷源的空间距离均值随回击间隔的增加而增大。 相似文献
10.
为了研究不同高度建筑物上发生的下行地闪回击特征差异,对2009—2012年广州高建筑物雷电观测试验中获取的能确认接地点高度的58次下行负极性地闪的综合同步观测资料进行对比分析。结果表明:接地点高度小于等于200m和接地点高度大于200m两类地闪的回击次数和回击间隔时间的差异不明显,但接地点高度大于200m的地闪的首次回击电流幅值、继后回击电流幅值、首次回击光强脉冲的10%~90%波前时间及10%波前~50%波后半宽时间、继后回击光强脉冲的10%~90%波前时间及10%波前~50%波后半宽时间的算术平均值 (几何平均值) 分别为接地点高度小于等于200 m地闪的1.8(2.1),1.5(1.4),7.4(7.4),3.1(3.4),4.6(4.3) 和2.4(3.6) 倍。 相似文献
11.
In this study we analyze the effects of continuing current initiated by strokes following a new channel to ground in multiple stroke flashes using high-speed video records, electric field measurements from a fast antenna and lightning detection network data. We observed that the long continuing current initiated by a stroke that follows a new channel also obeys the pattern in the initiation of long continuing current suggested by Rakov and Uman [Rakov, V.A., Uman, M.A., 2003. Lightning: Physics and Effects, 687pp., Cambridge Univ. Press, New York.]. We also verify that the statement of Rakov and Uman [Rakov, V.A. and Uman, M.A., 1990. Some properties of negative cloud-to-ground lightning flashes versus stroke order, Journal of Geophysical Research. 95, 5447–5453.] reporting that: “...strokes initiating long continuing currents tend to have lower initial electric field peak than regular strokes” is valid for strokes that create a new channel to ground and are followed by long continuing current (CC). Apparently the reduction of peak current value (Ip) when the stroke is followed by a long CC is stronger than the Ip increase that is commonly observed when strokes follow a new channel. We also find that the “exclusion zone” proposed by Saba et al. [Saba, M.M.F., Pinto, O. Jr., Ballarotti, M.G., 2006a. Relation between lightning return stroke peak current and following continuing current, Geophysical Research Letters 33, L23807, doi:10.1029/2006GL027455.] is valid for new channels initiating CC, and finally we verify that a number of strokes in the same channel larger than four or the existence of a long CC current do not always consolidate the channel in a multiple stroke flash. 相似文献
12.
2006年8月1日在广东省从化市利用成像率为5000幅/s的高速摄像系统观测得到了一次包含有13个回击过程的自然负地闪, 其梯级先导的传播速度为106 m/s的量级; 一次企图先导的传播速度随高度的降低而减小; 一次直窜先导的传播速度随高度的降低而增加。有3次继后回击相对积分亮度的峰值大于首次回击相对积分亮度的峰值。研究发现:此次自然闪电的继后回击及紧跟其后的连续电流过程的发光总量与该次继后回击之前闪电通道的截止时间有关, 较大的发光总量对应于较长的截止时间, 较小的发光总量对应于较短的截止时间, 但两者没有固定的比例关系。 相似文献
13.
Summary We have used a CGR3 lightning flash counter to gather lightning type and occurrence data over five complete years in Gaborone, Botswana. The results show that the mean ground flash density is 4.6 km–2 yr–1. Of these, 4.9% of ground flashes lower a net positive charge. The overall ratio of intracloud flashes to ground flashes is 1.9, the value being slightly higher during the nights than the daytime. A typical lightning season lasts from September to May, the activity reaching a peak between November and January. There is virtually no lightning at all during the dry winter months of June, July and August. The number of flashes per storm shows a marked decrease as the season progresses. In the diurnal cycle, the peak lightning activity occurs at around 19 h, which is somewhat late when compared with most other locations. However, together with observations in the Central United States, it seems to suggest that the peak activity occurs later in the day at mid-continental locations.With 7 Figures 相似文献
14.
Yijun Zhang Weitao Lu Jun Li Wansheng Dong Dong Zheng Shaodong Chen 《Atmospheric Research》2009,91(2-4):326-332
Using high-speed cameras, we have recorded the leaders contained in four natural negative cloud-to-ground (CG) lightning flashes in the summers of 2006 and 2007 at Conghua, Guangdong, China. It was found that the downward negative leaders preceding the first return stroke could propagate at quite different speeds. In one flash, the average speed of the downward negative stepped leader with no branches is about 2.2 × 106 m s− 1, while that of the other 3 flashes are all of the order of 105 m s− 1 with multilevel branches. The luminosity of the leaders shows an increasing tendency in propagating downward to the ground. For the leaders preceding the subsequent strokes, although all of them exhibit high speeds as reported previously. One subsequent leader exhibits an increasing speed from 5.2 × 105 m s− 1 to 1.7 × 106 m s− 1 during its propagation from about 1.26 to 0.36 km above the ground, and its luminosity also increased. The speed and luminosity of a leader between subsequent strokes of a natural lightning appear to decrease as it developed downward. Its speed ranges from 1.1 × 106 to 1.1 × 105 m s− 1, with a height between 1.15 and 0.81 km above the ground. 相似文献
15.
为研究不同高度的建筑物对雷电磁场的影响,对2011年7月—2012年8月广州高建筑物雷电观测试验中获取的雷电磁场波形数据进行统计分析,共选取击中14个高建筑物的40次雷电 (均为负极性雷电) 的磁场数据,结果表明:高建筑物对回击磁场峰值有增强作用,且建筑物越高对回击磁场峰值的增强作用越大,高度在200 m以上的建筑物上雷电首次回击磁场峰值的几何平均值是高度在200 m以下的建筑物上的2.4倍;高建筑物雷电回击的磁场波形呈多峰特征;观测到的20次击中200 m以下高建筑物的雷电中,有13次 (65%) 雷电首次回击的磁场波形出现后续峰值比初始峰值大的现象,击中200 m以上高建筑物的14次雷电中有8次 (57%) 出现该现象;40次高建筑物雷电中有22次 (55%) 为多回击雷电,135个回击间隔时间的几何平均值为69.1 ms, 多回击高建筑物雷电中有10次 (45%) 出现继后回击的磁场峰值大于首次回击磁场峰值的现象。 相似文献
16.
The seasonal variation of lightning flash activity over the Indian subcontinent (0°N–35°N and 60°E–100°E) is studied using the quality checked monthly lightning flash data obtained from lightning imaging sensor on board the Tropical Rainfall Measuring Mission satellite. This paper presents results of spatio-temporal variability of lightning activity over the Indian subcontinent. The study of seasonal total lightning flashes indicates that the lightning flash density values are in qualitative agreement with the convective activity observed over this region. Maximum seasonal total flash counts are observed during the monsoon season. The propagation of the inter-tropical convergence zone over this region is also confirmed. Synoptic conditions responsible for variation of lightning activity are also investigated with the help of an observed dataset. The mean monthly flash counts show a peak in the month of May, which is the month of maximum temperatures over this region. Maximum flash density (40.2 km?2 season?1) is observed during the pre-monsoon season at 25.2°N/91.6°E and the annual maximum flash density of 28.2 km?2 year?1 is observed at 33.2°N/74.6°E. The study of the inter-annual variability of flash counts exhibits bimodal nature with the first maximum in April/May and second maximum in August/September. 相似文献
17.
基于LMA三维闪电定位数据,对2004年10月5日发生于美国新墨西哥州的一次超级单体过程的闪电初始及其尺度特征进行研究,提出闪电初始阶段自动判别及其特征参量提取方法,并给出参量分布特征。结果显示:闪电初始阶段上行负先导（下行负先导）的持续时间中值为13.5 ms（7.5 ms）,三维位移中值为1.4 km（1.0 km）,三维平均位移速度中值为9.2×104 m·s-1（1.2×105 m·s-1）,上行负先导速度随时间递减,下行反之,二者与垂直方向夹角的中值分别为40°和54°。表征闪电尺度的闪电凸壳面积和闪电总长度的概率密度呈负幂函数分布,在小值方向分布更为集中。闪电水平延展距离中值为6.1 km,垂直延展距离中值为4.3 km,约83%的闪电其水平延展距离大于垂直延展距离;闪电的持续时间中值为271.0 ms。分析发现,以水平延展为主的闪电起始高度分布峰值位于8.5 km,以垂直延展为主的闪电起始高度分布峰值位于11 km。闪电初始阶段位移方向越接近水平,对应闪电垂直延展越小,说明闪电初始段的传播方向对于闪电垂直延展具有重要影响。 相似文献
18.
广东野外雷电综合观测试验十年进展 总被引：12，自引：0，他引：12
雷电野外科学试验是认识雷电发生、发展物理过程及其致灾机理的重要途径,也是开展真实雷电电磁环境下雷电防护技术测试的重要方式。自2006年开始,中国气象科学研究院和广东省气象局在广州野外雷电试验基地,持续合作开展了雷电野外综合观测试验,在人工触发闪电和自然闪电物理过程及其雷电防护技术测试试验等方面取得了若干研究结果。十年期间共成功触发闪电94次,回击电流峰值最大值为42 kA,平均值为16 kA;分析给出了自然闪电预击穿过程电场变化脉冲特征类型和差异;观测发现高建筑物上行连接先导可达几百米甚至超过1 km,其发展速度可达106 m/s量级,下行先导与上行连接先导的连接呈多样性;雷电防护技术测试试验表明人工触发闪电近距离电磁场耦合在架空线路上的感应电压达到千伏量级,多回击、长连续电流和地电位抬升是造成浪涌保护器(SPD)损害的主要因素;闪电定位系统探测性能的评估结果显示粤港澳闪电定位系统的闪电和回击的探测效率分别为96%和89%,定位误差算术平均值为532 m,回击电流强度的估算值约为真实值的0.63倍。 相似文献
19.
Lightning-generated nitrogen oxides(LNOx) have a major influence on the atmosphere and global climate change.Therefore, it is of great importance to obtain a more accurate estimation of LNOx. The aim of this study is to provide a reference for the accurate estimation of the total LNOx in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018. The energy of each CG flash was based on the number of return strokes per CG flash, t... 相似文献
20.
Over twenty thousand lightning location data obtained by using Lightning Location System (LLS) from Lanzhou and Beijing regions have been analysed to ascertain the characteristics of ground flashes in both regions. The strength of positive flashes is 5 times higher in Lanzhou than in Beijing. The strength of positive flashes is 3 times and 2.2 times as large as negative flashes in Beijing and in Lanzhou respectively. It has been found that the strength of positive and negative flashes is submitted to the normal distribution, and is independent of the characteristics of thunderstorm. So the lightning, strength obtained by DF may be used to forecast the coming of thunderstorm. Although the stroke number in both regions decreases as exponent regulation, the maximum number of return stroke for one lightning in Beijing is more than that in Lanzhou. The peak flash rate occurs in late afternoon for both regions, but the maximum and minimum flash rate appeared an hour earlier in Beijing than in Lanzhou.The relationship between DF display and lightning radiation electric field, discharge current is obtained. 相似文献