Estimation of Lightning-Generated NO_(x) in the Mainland of China Based on Cloud-to-Ground Lightning Location Data

Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study is to provide a reference for the accurate estimation of the total LNO_(x) 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,the peak current of each return stroke,and the assumed CG breakdown voltage.The energy of intracloud lightning(IC)was based on the estimated frequencies of IC and the assumed energy of each IC flash.Combining the energy of lightning and the number of nitric oxide(NO)molecules produced by unit energy(ρno),the total LNO_(x) production in the mainland of China was determined.The LNO_(x) in the mainland of China estimated in this study is in the range(0.157-0.321)×10^(9) kg per year[Tg(N)yr-1],which is on the high end of other scholars’works.Negative cloud-to-ground lightning(NCG)flashes produce the most moles of NO_(x),while positive cloud-to-ground lightning(PCG)flashes produce the least total moles of NO_(x).The breakdown voltage of PCG is greater than that of IC or NCG,while the latter has a greater output of LNO_(x).

Propagation of positive, negative, and recoil leaders in upward lightning flashes

Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.

The Characteristics of Cloud-to-Ground Lightning Activity with Severe Thunderstorm Wind in South and North China

The characteristics of cloud-to-ground(CG) lightning activity with severe thunderstorm wind(STW) in South and North China are analyzed using CG lightning data, radar data, and serious weather reports. The percentage of positive CG(PCG) flashes with STW in North China is larger than that in South China. STW takes place during the period when the total CG and PCG density is increasing fastest. STW also occurs close to the high-value center of CG and PCG density. In North China, the CG and PCG density in the grid of STW maximizes approximately 20 minutes after the STW occurs; while in South China, the PCG density and percentage of PCG in the grid of STW maximizes about 10 minutes before the occurrence of STW. The high-value centers of CG density and PCG density in North China move slightly faster than those in South China, which is opposite to the rate of increasing CG activity.

Temporal and Spatial Distribution of Lightning Activity in Ulanqab City

From January 2020 to December 2021,Ulanqab Meteorological Bureau of Inner Mongolia used VLF/LF lightning locator to carry out three-dimensional lightning monitoring in Ulanqab City,and compared with ADTD lightning location data in the same period.The results show that both VLF/LF lightning locator and ADTD lightning locator had excellent monitoring ability for lightning during flood season in Ulanqab.VLF/LF lightning locator was slightly superior to ADTD lightning locator in observation accuracy,the observation ability of low-current cloud-to-ground lightning,intracloud lightning observation and so on.There were obvious temporal and spatial characteristics of cloud-to-ground lightning during flood season in Ulanqab,and there was a certain correlation between the areas where lightning appeared frequently and surface water.Intracloud lightning was mainly concentrated at a height of 1-7 km.Negative cloud-to-ground lightning accounted for about 75%of total cloud-to-ground lightning,and negative intracloud lightning accounted for 39%of total intracloud lightning.

Characteristics of Cloud-to-ground Lightning during a Squall Line Process outside of the Subtropical High

Based on the monitoring data of cloud-to-ground( CG) lightning positioning network and Doppler weather radar as well as MICAPS1°× 1° objective analysis field,a squall line process outside of the subtropical high in low-latitude plateau on May 7,2010 was analyzed. The results showed that wind direction shear between low and high levels and low-level convergence zones provided favorable circulation background for the strong thunderstorm process,while high energy and high humidity,strong thermal instability and ascending motion at low and middle levels offered beneficial environmental conditions for the formation of the thunderstorm. 9 620 return strokes of cloud-to-ground lightning were monitored by the lightning positioning network,and cloud-to-ground lightning was distributed like bands between 584 and 586 hP a. The occurrence of cloud-to-ground lightning was mainly related to echo top and echo intensity at-10 ℃ stratification height,and it mainly appeared in zones where echo top height was larger than 13 km and echo intensity at-10 ℃ stratification height was 35-40 dB Z. Wind convergence and maintaining of high radial velocity were favorable for the development of convective echoes and occurrence of cloud-to-ground lightning.

Study on the Scope of Small Amplitude of Cloud-to-ground Lightning in Lightning Weather Monitoring

Based on lightning location data in Chongqing region during 1999-2008,the frequency of lightning in various amplitude ranges and its annual variations were analyzed firstly.Afterwards,with the aid of matlab mathematical software,the distribution of the lightning location data was fitted using logarithmic normal distribution function.The results showed that after data of cloud-to-ground lightning with current amplitude from-5 to5 kA were deleted from lightning location data,the statistical characteristics of cloud-to-ground lightning could be reflected well.Meanwhile,lightning with current amplitude from-5 to 5 kA accounted for 1.05%（less than 2%）,which accorded with the detection principle of lightning position indicator（there existed error detection）.Therefore,cloud-to-ground lightning with current amplitude of-5-5 kA in lightning location data of Chongqing region was defined as small amplitude of cloud-to-ground lightning,which could provide scientific references for the processing of lightning location data in Chongqing region as well as analysis and quality control of lightning location data in other regions.

Studies on the Distribution Characteristics of the Cloud-to-Ground Lightning and Its Disasters Prevention in Xinjiang, China in 2017

Xinjiang, China is affected by geographical terrain and other factors, and is prone to lightning disasters. In order to effectively carry out lightning protection and disaster reduction work and improve defense capabilities, based on the data of lightning location monitoring in Xinjiang in 2017 and the statistics reports of the lightning disasters from 2015 to 2017, the characteristics of the cloud-to-ground (CG) lightning activities and disasters in Xinjiang were statistically analyzed. The results show that the CG lightning in Xinjiang is mainly the negative one, accounting for 79.7% of the total lightning. In 2017, the distribution of positive, negative and total the CG lightning months mainly focuses on June to August, and the main occurrence period is from 14 to 23 hours. The intensity of total the CG lightning and negative the CG lightning mainly distributes from 20 to 40 kA, and the peak value appears in 30 kA. The CG lightning intensity is mainly distributed in 30 - 70 kA. The distribution of the CG lightning density in Xinjiang is larger in the north than in the south and larger in the west than in the east. Lightning disasters mainly occur from May to August, accounting for 93.2 percent of the total, with the largest number in June. From 2005 to 2017, 44.6% of lightning accidents occurred in farming and pastoral areas, followed by civil electronic equipment damage. In addition, electrical equipment, buildings and factory equipment are damaged by lightning strikes to varying degrees.

Characteristics of Cloud-to-ground Lightning during a Local Rainstorm in Meizhou City

Based on cloud-to-ground lightning data of lightning location system,Doppler radar data,and precipitation data of regional automatic weather stations,the characteristics of cloud-to-ground lightning during a local rainstorm on June 4,2016 in Meizhou City were analyzed. The results showed that the spatial distribution of cloud-to-ground lightning from 14： 00 to 20： 00 on June 4,2016 in Meizhou City had obvious local characteristics,and the proportion of negative lightning was larger than that of positive lightning（ only 16. 8%）. The concentration period of positive lightning coincided with that of cloud-to-ground lightning. The peak of proportion of positive lightning lagged behind the peak of cloud-to-ground lightning,and appeared in the late period of thunderstorm disappearance. The dense area of cloud-to-ground lightning and the area with heavy rainfall coincided with the area with strong radar echoes. Doppler weather radar data had the feature of the headwind zone,strong combined reflectivity,vertical height of strong echoes,high echo top,and fast radial movement. The peak of cloud-to-ground lightning appeared one hour earlier than that of precipitation. There was no significant correlation between the frequency of cloud-to-ground lightning and precipitation. The peak of negative lightning corresponded to that of positive lightning,and cloud-to-ground lightning ended earlier than rainfall. After the peak of precipitation,convective system rapidly weakened and disappeared. Precipitation and the frequency of cloud-to-ground lightning fluctuated frequently during the whole process. The jumps and peaks of negative lightning were indicative of rainfall changes.

Review of the Lightning Shielding Against Direct Lightning Strokes Based on Laboratory Long Air Gap Discharges

长间隙放电是研究地面物体雷电屏蔽问题的最有效手段之一。首先介绍了国内外在雷电击距、直击雷防护措施的屏蔽性能试验和雷电迎面先导过程研究3个方面所取得的进展，并结合最新开展的长达6m问隙尺度的放电试验观测，对现阶段上述3个方面研究所存在的问题进行了分析。认为基于雷电击距建立的电气几何模型（electricgeometrymodel，EGM）仅适用于小尺度目标物的雷电屏蔽性能分析，现有的雷电屏蔽模拟试验方法仅能近似模拟不存在雷电迎面先导时的雷击过程，无法完全证明以提前流注发射模型装置为代表的非传统防雷装置具有比传统措施更优越的屏蔽性能。大尺度目标物的雷电屏蔽问题应聚焦于雷电迎面先导过程的研究，建立并完善雷电迎面先导过程的模拟试验方法和物理仿真模型。

Discharge characteristics of different lightning air terminals under composite voltages

Different types of lightning air terminals have been designed over the years.Concern regarding the effect of different types of air terminals,especially the early streamer emission(ESE)-type,remains controversial.This paper describes the discharge characteristics of different types of air terminals,two of which are quite similar to the ESE-type dynasphere,and concludes that the tested non-standard air terminals have discharge characteristics similar to those of Franklin rods and that their lightning protection performance should be similar.

Effectiveness of Lightning Protection Devices

In addition to the conventional Franklin Rod,many non-conventional air terminals are being used as lightning protection devices.As cited in previous works,these non-conventional devices emit space charge in the vicinity of the terminals during the process of lightning stroke.A number of factors affect the performance of these lightning protection devices,among them are geometry and dimension of the devices,location of the device above the ground,height of the cloud above the ground,and polarity of the lightning stroke.The performance of these lightning protection devices has been a topic of discussion by researchers for many years.Some studies focused on the magnitude of emission current from these devices as a criterion to evaluate their performances.The critical flashover voltage(CFO)between the devices and a metal screen simulating cloud can also be used as another criterion to evaluate the performance of the devices.Laboratory measurements were conducted in controlled conditions on different types of lightning protection devices to compare their performance.Four different types of devices were used in the present study:Franklin Rod,TerraStat models TS 100,TS 400,and Spline Ball Ionizer.The study focused on the CFO voltage of the air gap between devices and the metal screen.The CFO voltage was evaluated using standard switching and lightning impulses.The measurements were recorded for positive as well as negative polarity.The air gap between the devices and metal screen was selected at 2 m and 3 m.The results obtained provide a better understanding of the electrical performance of lightning protection devices.

THE STATISTIC RELATION BETWEEN LIGHTNING AND CINRAD DOPPLER RADAR ECHOES IN CENTRAL GUANGDONG

Based on the CINRAD Doppler radar data in Guangzhou and the lightning data in 2004 by power suppliers of Guangdong, statistical study is done by overlaying lightning＇s position on radar＇s echo. The result shows the followings. The concentrated period in which more negative lightning occurred at the middle levels （2 - 14 km）, where radar echo was moderate （12 - 45 dBz）, rather than at the low levels with the weakest echoes or at high levels with the strongest echoes. At levels 3 - 11 km, where the radar echo was between 10 dBz and 35 dBz, the area of negative lightning was much larger in central Guangdong than in the rest of the province. At levels 0.5 - 7 krn where the radar echoes were between 44 dBz and 51 dBz, the probability for a point to have negative lightning varies from 0.4 to 0.7.

Modeling of Lightning Shielding Failure in UHV Transmission Line Based on Randomness Theory

The operation data obtained abroad indicates that shielding failure in UHV transmission lines mostly accounts for the tripping-out accidents introduced by lightning striking the transmission line.Based on the discharge theories of long air gap and randomness theory,a leader progression model of lightning shielding failure is presented in this paper.The random characteristics of the downward and upward leader are simulated in this model.The ground slope angel is also considered in this model by using coordinate transformation.Moreover,the system voltage is also taken into consideration in this model.The simulation results show that the good agreement between this model and the field data.And the results suggest that return striking exist obviously in UHV transmission line.

超/特高压输电线路雷电绕击分析方法及其适应性

输电线路雷击已成为制约电力系统安全可靠运行的首要因素,而500 kV及以上电压等级的输电线路主要以雷电绕击导线为主。该文在回顾电气几何模型发展历史的基础上,针对电气几何模型忽略大部分雷击物理过程的问题,详细分析先导发展法,包括雷击输电线路物理过程、先导发展模型参数选择、数值方法实现及模型验证,该方法能够全面模拟雷击发展的物理过程;最后,采用先导发展法分析影响线路绕击特性的因素,并讨论不同绕击分析方法的适用范围,对于500 kV及以上的超特高压线路以及同塔多回输电线路,宜采用先导发展法分析雷电绕击。该研究可为输电线路防雷设计及运行事故分析提供关键技术支撑。

Optical Observations on Propagation Characteristics of Leaders in Cloud-to-Ground Lightning Flashes

Using 2 high-speed cameras, we have recorded 14 negative cloud-to-ground （CG） lightning flashes, half of which are natural and the others are artificially triggered. The two-dimensional （2D） propagation speed of different type leaders and the luminosity of lightning channel are analyzed in detail. Bidirectional leader processes are observed during the initial processes of two altitude triggered negative lightning （ATNL） flashes. The analysis shows： the propagation speed of the upward positive leader （UPL） before the initiation of the downward negative leader （DNL） is at the order of 10^4-10^5 m s-1; the UPL can be intensified by the initiation and development of the DNL in the way that the luminosity is enhanced and the speed is sped up; after initiation, the DNL in one ATNL flash propagates downward three times intermittently with interval of about 1 ms, while that in the other ATNL flash propagates downward continuously with a speed at the order of 10^5 m s^-1. In the five classical triggered negative lightning （CTNL） flashes, the propagation speeds of the UPLs vary between 0.35×10^5 and 7.71×10^5 m s-1, and the variations of their luminosities and speeds are quite complex during the development processes. Among the four observed natural negative lightning flashes occurred on the land, three have only one return stoke （RS） each and all of their DNLs have many branches with an average speed at the order of 10^5 m s-l; while the another one has 13 RSs. In the CG flash with 13 RSs, the DNL before the first RS has no obvious branch below 1.4 km above the ground, and its speed ranges from 2.2×10^5 to 2.3×10^6 m s-1 between the heights of 0.7 and 1.4 km and exceeds 3.9×10^6 m s-1 below 0.7 km; preceding the 4th RS, an attempted leader is observed with a speed ranging from 1.1× 10^5 to 1.1×10^6 m s-1 between 0.8 and 1.5 km. As for the three observed natural negative lightning flashes occurred on the sea, each has only one RS, and each DNL preceding the RS has a few branches, two of which have an average propagation speed at the order of 10^5 m s-1, and the other of 10^6 m s-1, respectively. All the DNLs contained in the observed natural negative lightning flashes, except the attempted leader, propagate with gradually increasing luminosity and increasing speed in whole.

正极性人工触发闪电的向上负先驱脉冲放电过程研究

利用人工触发正极性闪电的综合同步探测资料,对引雷火箭上升过程中发生于金属导线顶端的向上负先驱脉冲放电过程进行了研究。除常规认识的峰值电流为十几到几十安培的先驱脉冲放电以外,高垂直分辨率电流探测系统记录到丰富的弱脉冲放电过程。所有孤立发生的脉冲放电,均为弱脉冲,且在所有常规强度的先驱脉冲(簇)放电之前约20μs,均识别到这种弱脉冲。对测量到的弱脉冲、脉冲型脉冲和波纹型脉冲进行统计,得到了各自的峰值电流(3.6 A、32.2 A、11.1 A)、上升时间(0.39μs、0.9μs、3.2μs)、持续时间(2.8μs、5.1μs、12.7μs)和转移电荷量(4.7μC、50.8μC、83.2μC)。常规强度的先驱脉冲形成了可探测的发光通道,簇状先驱脉冲的放电通道具有与自持先导初始阶段相一致的梯级发展传输特征,二维平均速度在105 m s^(−1)量级。分析相邻先驱脉冲发光通道的时空关系,发现后一次先驱脉冲放电通道的起始高度一般位于前一次先驱脉冲放电通道的顶端,通道梯级延伸时电荷分布的调整降低了通道区域的电场强度。先驱脉冲放电是金属导线顶端形成了先导但又由于条件不足而熄灭的过程。

基于TEROS的自然闪电X射线暴观测研究

本文报道了国内首个自然闪电高能辐射(Lightning Energetic Radiation,LER)多点观测结果.基于自主研发的雷暴高能辐射观测系统(Thunderstorm Energetic Radiation Observation System,TEROS),在2021年夏季观测期成功捕获3次自然LER事件,结合闪电定位、低频快电场变化、回击峰值电流等其他资料,对3次事件的高能辐射特征进行研究.分析发现:3次LER事件均于负地闪下行先导的最后阶段被探测到,是典型的X射线暴,且均具有MeV能量的单光子,最大能量超过2.2 MeV;伴随梯级先导出现的X射线暴持续时间为数百μs,伴随不规则直窜先导的X射线暴持续时间为数十μs,主要与先导发展速度有关;相应回击峰值电流最大的1次事件具有最高的单光子能量、最大的单位面积沉积总能量和最多的爆发过程数量,随着接近回击时刻,该事件还表现出与电场变化一致的增强趋势,表明先导头部电场是影响高能辐射产生的重要因素;随到达强度降低,高能辐射信号逐渐由束流模式向单光子模式转变,呈现出与地球伽马射线闪类似的现象学特征,更多乃至所有的爆发过程无法被探测到,高能辐射可能是闪电发展过程中的普遍现象.

1m级间隙正极性雷电冲击闪络判据海拔校正方法的适用性

绝缘子及空气间隙的雷电冲击闪络判据是评估输电线路耐雷性能的重要仿真模型之一,同一间隙的闪络判据在不同海拔地区应用需要进行海拔校正。绝缘子及空气间隙的雷电冲击U50%闪络判据可以采用g参数进行海拔校正,但是更加精确的闪络判据如伏秒特性及先导发展模型法尚缺乏有效的海拔校正方法。该文针对110kV线路用复合绝缘子及1m棒-板间隙,分别在平原和高海拔地区开展了正极性标准雷电冲击试验,对比了海拔对冲击闪络特性的影响,分析了现有海拔校正方法在U50%及伏秒特性散点校正中存在的问题。然后,拟合了适用于不同海拔的110 kV单支复合绝缘子及1 m棒-板间隙的正极性标准雷电波先导发展模型,并将该模型计算得到的U-t曲线与试验所得的伏秒特性散点进行对比分析,验证了先导发展模型通过改变相对空气密度开展闪络判据海拔校正的适用性。最后,通过对比分析不同先导发展模型对计算110kV输电线路耐雷水平的影响,证明了先导发展模型闪络判据海拔校正的精确性。

建筑物顶端几何特征对上行先导起始影响的3D模拟

建筑物几何特征对上行先导始发具有重要影响,基于三维变网格雷击物理模型,在不同几何特征建筑物和不同雷电流峰值情况下,探讨了下行负地闪过程中,建筑物顶部上行正先导始发影响因素。除了发现建筑物高度对先导的始发具有促进作用外,还得到以下结论:①雷电流峰值I_(P)相同时,建筑物的高度越高,其几何形状对上行稳定先导起始的影响(η)就越小。建筑物高度相同时,雷电流峰值越大,η越小;②圆柱塔形尖端的上行稳定先导最容易起始,且最接近针形,η最小,为12.2%。长方体形上的稳定先导起始最晚,η最大,可达53.4%;③对于高度较矮和雷电流峰值较小的情况下,尖端几何形状(塔形或斜坡)对先导起始的影响较明显。