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

Acta meteorologica Sinica 2008年第1期22卷 66-77页

作者：吕伟涛张义军李俊郑栋董万胜陈绍东王飞 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences

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 branc

关键词： cloud-to-ground lightning propagation speed of leader luminosity of lightning channel highspeed photography

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Simulation Study About the Influence of Atmospheric Stratification on lightning Activities

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Acta meteorologica Sinica 2008年第1期22卷 78-90页

作者：郑栋张义军吕伟涛马明孟青 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences

A 2D model about charging and discharging processes in thundercloud is used to simulate three differential atmospheric stratifications resulting in discrepant thunderstorm processes in Beijing region. The dynamic and microphysical processes in thunderstorm and their influence on lightning activities are also discussed. The results indicate that ascending velocity and water vapor are the most important factors to influence lightning activities. At the same time, they affect each other and are together controlled by atmospheric stratification. The magnitude of the ascending velocity determines the intensity of storm and the time when the thunderstorm matured. The thunderstorm with strong updrafts can reach a large height in a short time. Strong persistent updrafts and sufficient water vapor which help to generate more ice phase hydrometeors that directly influence charging and discharging process will prolong the mature stage of the thunderstorm and thereby enhance lightning activities. Though the big density of ice phase hydrometeors can be formed, it is difficult to sustain a long time in the condition of strong updrafts and scant water vapor. Under the condition of weak updrafts and sufficient water vapor in the whole levels, it is easy to form warm cloud process in which the ice phase process and lightning activities are weak. The favorable stratification conditions for strong lightning activities are the sufficient vapor in the lower atmosphere, moderate humidity in the mid troposphere. big instability energy and some suitable convective inhibition. Through calculating some atmospheric instability parameters, it is indicated that convective instability index smaller than -10℃ （negative means instable）, convective available potential energy larger than 1000 J kg-1, convective inhibition larger than 40 J kg-1 the 700-hPa potential equivalent temperature larger than 340 K and the 35%-85% humidity in the mid troposphere （700-400 hPa） are the advantageous conditions f

关键词： atmospheric instability parameters model hydrometeor electric structure

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Total lightning Characteristics and Electric Structure Evolution in a Hailstorm

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Acta meteorologica Sinica 2009年第2期23卷 233-249页

作者：郑栋张义军孟青吕伟涛易笑园 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences Tianjin Meteorological Bureau

In this paper, total lightning data observed by SAFIR3000 3-D lightning Locating System was combined with radar data to analyze characteristics of the lightning activity and electric structure of a hailstorm that occurred in Beijing on 31 May 2005. The results indicated that there were two active periods for the lightning activity during the hailstorm process. The hail shooting was found in the first period. After the end of the hail shooting, lightning frequency decreased suddenly. However, more active lightning activities occurred in the second period with lots of them appearing in the cloud anvil region. The peak of the lightning frequency came about 5 min prior to the hail shooting. Only 6.16% of the total lightning was cloud-to-ground （CG） lightning, among which 20% had positive polarity. This percentage was higher than that in normal thunderstorms. In addition, heavier positive CG lightning discharge occurred before rather than after the hail shooting. In the stage of the hail shooting, the electric structure of the hailstorm was inverted, with the main negative charge region located around the -40℃ level and the main positive charge region around the -15℃ level. In addition, a weak negative charge region existed below the positive charge region transitorily. After the hail shooting, the electric structure underwent fast and persistent adjustments and became a normal tripole, with positive charge in the upper and lower levels and negative charge in the middle levels. However, the electric structure was tilted under the influence of the westerly wind in the middle and upper levels. The lightning activity and electric structure were closely related to the dynamic and microphysical processes of the hailstorm. It was believed that severe storms with stronger updrafts were more conducive to an inverted tripolar electric structure than normal thunderstorms, and the inverted distribution could then facilitate more positive CG lightning in the severe storms.

关键词： lightning activity electric structure non-inductive charging mechanism bidirectional leader

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Impact of Updraft on Neutralized Charge Rate by lightning in Thunderstorms:A Simulation Case Study

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Journal of Meteorological Research 2015年第6期29卷 997-1010页

作者：王飞张义军郑栋 State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences(CAMS) Laboratory of Lightning Physics and Protection Engineering CAMS

The rate of neutralized charge by lightning（RNCL） is an important parameter indicating the intensity of lightning *** total charging rate（CR）,the CR of one kind of polarity（e.g.,negative） charge（CROP）,and the outflow rate of charge on precipitation（ORCP） are proposed as key factors impacting RNCL,based on the principle of conservation of one kind of polarity charge in a *** this paper,the impacts of updraft on CR and CROP are analyzed by using a 3D cloud resolution model for a strong storm that occurred in Beijing on 6 September *** results show that updraft both promotes and inhibits RNCL at the same time.（1） Updraft always has a positive influence on *** correlation coefficient between the updraft volume and CR can reach *** of the updraft facilitates strengthening of RNCL through this positive influence.（2） Strengthening of the updraft also promotes reinforcement of *** correlation coefficient between the updraft volume and CROP is high（about0.9）,but this promotion restrains the strengthening of RNCL because the strengthening of CROP will,most of the time,inhibit the increasing of RNCL.（3） Additionally,increasing of ORCP depresses the strengthening of *** terms of magnitude,the peak of ORCP is equal to the peak of *** precipitation mainly appears after the lightning activity finishes,the depression effect of ORCP on RNCL can be ignored during the active lightning period.

关键词： lightning activity updraft neutralized charge charging rate charge amount

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Impact of the Vertical Velocity Field on Charging Processes and Charge Separation in a Simulated Thunderstorm

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Journal of Meteorological Research 2015年第2期29卷 328-343页

作者：王飞张义军郑栋徐良韬 State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences

A three-dimensional（3D） charging-discharging cloud resolution model was used to investigate the impact of the vertical velocity field on the charging processes and the formation of charge structure in a strong thunderstorm. The distribution and evolution of ice particle content and charges on ice particles were analyzed in different vertical velocity fields. The results show that the ice particles in the vertical velocity range from 1 to 5 m s-1obtained the most charge through charging processes during the lifetime of the thunderstorm. The magnitude of the charges could reach 1014 n C. Before the beginning of lightning activity,the charges produced in updraft region 2（updraft speed 13 m s-1） and updraft region 1（updraft speed between 5 and 13 m s-1） were relatively significant. The magnitudes of charge reached 1013 n C, which clearly impacted upon the early lightning activity. The vertical velocity conditions in the quasi-steady region（updraft speed between -1 and 1 m s-1） were the most conducive for charge separation on ice particles on different scales. Accordingly, a net charge structure always appeared in the quasi-steady and adjacent regions. Based on the results, a conceptual model of ice particle charging, charge separation, and charge structure formation in the flow field was constructed. The model helps to explain observations of the＂lightning hole＂ phenomenon.

关键词： vertical velocity field charging processes charge separation lightning cloud resolution model

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Climatology of lightning Activity in South China and Its Relationships to Precipitation and Convective Available Potential Energy

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Advances in Atmospheric Sciences 2016年第3期33卷 365-376页

作者： Dong ZHENG Yijun ZHANG Qing MENG Luwen CHEN Jianru DAN State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological SciencesBeijing 100081 Lightning Protection Center of Guangdong Province Guangzhou 510080 Conghua Meteorological Bureau Guangzhou 510925

This study examined lightning activity and its relationship to precipitation and convective available potential energy （CAPE） in South China during 2001-12, based on data from the Guangdong lightning Location System, the Tropical Rainfall Measuring Mission satellite, and the ERA-Interim dataset. Two areas of high lightning density are identified： one over the Pearl River Delta, and the other to the north of Leizhou Peninsula. Large peak-current cloud-to-ground （LPCCG） lightning （〉75 kA） shows weaker land-offshore contrasts than total CG lightning, in which negative cloud-to-ground （NCG） lightning occurs more prominently than positive cloud-to-ground （PCG） lightning on land, While the frequency of total CG lightning shows a main peak in June and a second peak in August, the LPCCG lightning over land shows only a single peak in June. The ratio of positive LPCCG to total lightning is significantly greater during February-April than during other times of the year. Diurnally, CG lightning over land shows only one peak in the afternoon, whereas CG lightning offshore shows morning and afternoon peaks. The rain yield per flash is on the order of 107-108 kg per flash across the analysis region, and its spatial distribution is opposite to that of lightning density. Our data show that lightning activity over land is more sensitive than that over offshore waters to CAPE. The relationships between lightning activity and both precipitation and CAPE are associated with convection activity in the analysis region.

关键词： climate characteristics lightning precipitation CAPE large peak current land-offshore contrast

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Correlation Between Total lightning Activity and Precipitation Particle Characteristics Observed from 34 Thunderstorms

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Acta meteorologica Sinica 2010年第6期24卷 776-788页

作者：郑栋孟青张义军戴建华钟敏 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences Shanghai Meteorological Center Hubei Provincial Meteorological Bureau

A total of 34 thunderstorms around Shanghai and Wuhan of China are analyzed in order to determine the relationship between total lightning activity and precipitation particle *** particle concentration data are obtained from the 2A12 product of TRMM/TMI（Tropical Rainfall Measuring Mission/TRMM Microwave Image） and lightning activity data are from the TRMM/LIS（lightning Imaging Sensor） and SAFIR3000（Surveillance et Alerte Founder par Interferometric Radioelectirque）.On a spatial scale of 0.1°×0.1°,a weak spatial relationship is found between total lightning and the vertically integrated content（VIC） of precipitation particles（cloud water,precipitation water,cloud ice,and precipitation ice）. A strong power relationship is identified between the lightning density（D_（30）;fl km^（-2） min^（-1））,relative to a rainfall intensity threshold value of 30 mm h^（-1）,and the maximum rainfall intensity（R_（max）;mm h^（-1））;the obtained regression equation is R_（max） = 23.10D_（30）^（0.18）＋ 11,with a correlation coefficient of *** frequency shows a significant linear correlation with the contents and covering areas of precipitation particles （in which the VICs exceed threshold values）.Furthermore,ice particles above the -10℃level exhibit a stronger correlation with lightning activity than those above the 0℃level or the integrated ice particles at all *** results demonstrate that the particles responsible for the most significant charging process and lightning activity are restricted by the threshold value of VIC among the particles,which reflects the demand of the charging process on dynamic *** obtained fitting equations can provide useful reference for assimilating lightning information into numerical prediction models so as to improve the reliability of forecast *** particle products from the prediction models are also helpful in estimating the occurrence of lightning activity within 2-6-h periods.

关键词： lightning activity precipitation particles correlation TRMM

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Analysis of Channel Luminosity Characteristics in Rocket-Triggered lightning

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Acta meteorologica Sinica 2008年第3期22卷 362-374页

作者：吕伟涛张义军周秀骥孟青郑栋马明王飞陈绍东郄秀书 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences State Key Laboratory of Severe Weather(LaSW) Chinese Academy of Meteorological Sciences Lightning Protection Center of Guangdong Province Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

A comparison is made of the high-speed （2000 fps） lightning between two techniques. The analysis shows （UPL） in altitude-triggered negative lightning （ATNL） photographic records in rocket-triggered negative that： the initial speed of upward positive leader is about one order of magnitude less than that in classically triggered negative lightning （CTNL）, while the triggering height of ATNL is higher than that of CTNL; the afterglow time of metal-vaporized part of the lightning channel can endure for about 160-170 ms, thus the luminosity of the air-ionized part can reflect the characteristics of the current in the lightning channel better than that of the metal-vaporized part. According to the different characteristics of the luminosity change of the lightning channel, together with the observation of the electric field changes, three kinds of processes after return-stroke （RS） can be distinguished： the continuous decaying type without M component, the isolated type and the continuing type with M component, corresponding to different wave shapes of the continuous current. The geometric mean of the interval of RS with M component is 77 ms, longer than that （37 ms） of RS without M component. And the initial continuous current （ICC） with M component also has a longer duration compared to the ICC without M component. The distinction in the relative luminosity between the lightning channel before RS and that before M component is obvious： the former is very weak or even cannot be observed, while the latter is still considerably luminous.

关键词： rocket-triggered lightning high-speed photography lightning channel luminosity characteristics

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The role of dynamic transport in the formation of the inverted charge structure in a simulated hailstorm

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Science China Earth Sciences 2016年第7期59卷 1414-1426页

作者： XU Liang Tao ZHANG Yi Jun LIU Heng Yi ZHENG Dong WANG Fei State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences College of Earth Sciences University of Chinese Academy of Sciences Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences

The inverted charge structure formation of a hailstorm was investigated using the Advanced Weather Research and Forecasting(WRF-ARW) model coupled with electrification and discharge schemes. Different processes may be responsible for inverted charge structure in different storms and regions. A dynamical-derived mechanism of inverted charge structure formation was confirmed by the numerical model: the inverted structure was formed by strong updraft and downdraft under normal-polarity charging conditions such that the graupel charged negatively in the main charging region in the middle-upper level of the cloud. The simulation results showed the storm presented a normal charge structure before and after hail-fall; while during the hail-fall stage, it showed an inverted charge structure—negative charge region in the upper level of the cloud and a positive charge region in the middle level of the cloud—appearing at the front edge near the strong updraft in the hailstorm. The charging processes between the two particles mainly occurred at the top of the cloud, where the graupel charged negatively and ice crystals positively due to the strong updraft. When the updraft air reached the top of the storm, it would spread to the rear and front. The light ice crystals were transported backward and forward more easily. Meanwhile, the positively charged ice crystals were transported downward by the frontal subsidence, and then a positive charge region formed between the ?10 and ?25°C levels. Subsequently, a negative charge region materialized in the upper level of the cloud, and the inverted charge structure formed.

关键词： Severe storm Mesoscale model Inverted charge structure

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Semi-Idealized Modeling of lightning Initiation Related to Vertical Air Motion and Cloud Microphysics

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Journal of Meteorological Research 2017年第5期31卷 976-986页

作者： fei wang yijun zhang dong zheng liangtao xu wenjuan zhang qing meng state key laboratory of severe weather chinese academy of meteorological sciencesBeijing 100081 laboratory of lightning physics and protection engineering chinese academy of meteorological sciencesBeijing 100081

A three-dimensional charge^lischarge numerical model is used, in a semi-idealized mode, to simulate a thunder- storm cell. Characteristics of the granpel microphysics and vertical air motion associated with the lightning initiation are revealed, which could be useful in retrieving charge strength during lightning when no charge^diseharge model is available, The results show that the vertical air motion at the lightning initiation sites （Wini） has a cubic polynomial correlation with the maximum updraft of the storm cell （WceH_m^x）, with the adjusted regression coefficient R2 of ap- proximately 0.97. Meanwhile, the graupel mixing ratio at the lightning initiation sites （qg-ini） has a linear correlation with the maximum graupel mixing ratio of the storm cell （qg-cell-max） and the initiation height （Zini）, with the coeffi- cients being 0.86 and 0.85, respectively. These linear correlations are more significant during the middle and late stages of lightning activity. A zero-charge zone, namely, the area with very low net charge density between the main positive and negative charge layers, appears above the area of qg-oewm and below the upper edge of the granpel re- gion, and is found to be an important area for lightning initiation. Inside the zero-charge zone, large electric intensity forms, and the ratio of qice （ice crystal mixing ratio） to qg （graupel mixing ratio） illustrates an exponential relation- ship to qg-ini. These relationships provide valuable clues to more accurately locating the high-risk area of lightning initiation in thunderstorms when only dual-polarization radar data or outputs from numerical models without char- ging/discharging schemes are available. The results can also help understand the environmental conditions at light- ning initiation sites.

关键词： lightning initiation graupel ice crystal vertical air motion cloud microphysics

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