Current Issue

• Observation on the Summer Lightning Discharge in the Northeastern Verge of Qinghai-Xizang Plateau
• QIE Xiu-shu;ZHANG Guang-shu;KONG Xiang-zhen;ZHANG Yi-jun;WANG Huai-bin;ZHOU Yun-jun;ZHANG Tong;WANG Su-ju
• 2003 Vol. 22 (3): 209-216. 
• Abstract ( ) PDF (400KB) ( )
• In the summer of 2002,a comprehensive observation on natural lightningdischarges was conducted in the northeasternverge of Qinghai-XizangPlateau.The average altitude on the observation area is about 2650 m.During the experiment,field mill,fast and slow antenna systems were employed in 6 sites synchronized by GPS with 0.4 μs time resolution.Meanwhile,high speed video camera with 1 ms resolution was used in the observation.The preliminary study shows that the polarity of electric field underneath thunderstorm could be positive or negative with positive is more often,indicating the complexityof the thunderstorm charge structure in this area.The lightning discharge shows some special characteristics with corresponding to the complex of charge structure andspecial topography.The stepped leader usually develops downward to ground with multi-branches with a 2-D velocity of about 0.8~1.2×10 ⁵ m·s ^-1.Because of the multi-branches of the stepped leader,more than one striking point on the ground was often observed as a result.Long intracloud(IC) discharges will occurnot onlyjust before the ground discharge but also after the ground discharge.The pictures from high videocamera confirmed the bi-level structure of IC discharge,as observed by interferometerand TOA observation.The IC discharge initiates excitation between upper negative charge region and lower positive charge region,and developed downward and upward to the lower positive and upper negative region,respectively.After the main vertical channel setup,the discharge developshorizontally in the lower positive charge region with more branches.In the final stage,the discharge in the upper channel developshorizontally in the negative charge region.

• Three Dimensions Structure of Lightning Discharge Channel
• ZHANG Yi-jun;Paul R. Krehbiel;LIU Xin-sheng;ZHANG Guang-shu
• 2003 Vol. 22 (3): 217-220. 
• Abstract ( ) PDF (960KB) ( )
• The three-dimensional spatial and temporal development of impulsive VHF radiation eventsduring lightning discharges have been analyzed based on thedata measured by lightning mapping array(LMA) system with high spaceand time resolution.The resultsindicate that intracloud discharges(IC) and cloud-to-ground discharge(CG) can reveal the basic charge structure of thunderstorm.The intracloud dischargesoccured not only between the upper positive andlowernegative charge region,but also between lower positive and uppernegative charge region.Their characteristics were similar except for the opposite polarity.The channels of IC lightning propagated upward for normal and downward for invert during initial stage with 10~20 ms in time.After that,the channel changed to propagate horizontally in positive charge region.There were much more radiation points in positive charge region and lightning channel which clear.While there were less radiation points and lightning channels were extended from the starting point of lightning in a retrograde manner horizontally in negative charge region. K type breakdown appeared not only in last stage of IC lightning,but also in active stage and developed into positive charge region.The K type breakdown sometime triggered new channels in positive charge region.The negative step leaders produced intense radiation and dart leaders produced weak radiation for negative CG.The channels of negative CG lightning developed horizontally and produced a lot of small branches between return strokes.Some attempt leaders occurred during this period.The positive leaders produced no radiation.There were the development processes with long lasting time in cloud before and after positive return stroke.The characteristics of positive CG lightning were differed from that of negative CG lightning.This revealed that there were different breakdown mechanismsbetween positive and negative CG lightning.

• Propagation of the Lightning Channel and Electromagnetic Radiation in IC Flashes
• DONG Wan-sheng;LIU Xin-sheng;ZHANG Yi-jun;WANG Huai-bin
• 2003 Vol. 22 (3): 221-225. 
• Abstract ( ) PDF (275KB) ( )
• Radio frequency observations of intracloud(IC) lightning were made in Guangdong of China in 1999,with the broadband lightning interferometer.The spatial and temporal variations of radiation sources,the spectra and associated electric field change have been analyzed in this paper.The intracloud discharge could be divided into both the active and finally stages according to the waveforms of the intracloud lightning.The locations of the radiation sources indicate that the intracloud lightning is initiated usually by a negative breakdown processes upwards,and the upwards propagation speed of the lightning channel is about 3~3.3×10 ⁵ m·s ^-1.The main channel of the intracloud discharge is formed during its active stage.The characteristics of the spatial and temporal variations of radiation sources and the electric field change caused by lightning discharge indicate that the primary charge in thunderstorm has a distribution of positive electricaldipole.During the finally stage of the intracloud,the radiation sources appear mainly in thepreviously formed channel and is similar to the characteristics of the radiation sources in return stroke of the cloud-to-ground lightning.The spectra radiated by lightning discharged have peaks in the frequency interval from 2 to 3 MHz and the intensity of radiation reduce with the frequency.

• Short-Baseline Time-of-Arrival Lighting Radiation Detection System and Preliminary Location Result
• ZHANG Quan;QIE Xiu-shu;ZHANG Guang-shu
• 2003 Vol. 22 (3): 226-234. 
• Abstract ( ) PDF (357KB) ( )
• This paper introduced a new developedlighting detection equipment:Short-baseline time-of-arrival lighting radiation detection system.The system has been used in the lightingobservation experimentin the summer of 2002.Two cloud-to-ground(C-G) lighting dischanges and two intracloud(IC) lighting discharges are analyzed in this paper,respectively,by combining the characteristic of electric field change.The results indicated that this system works well for the radiation produced by IC lighting and the stepped leader of C-G lighting.It has been found that the discharge processes of two IC lighting in the observation region were initiated by the negativepolarity breakdown started from the negative charge area in the lower part of the cloud,then progressed upward to the positive charge area in the upper part of the cloud.The progression velocity of the discharge channelwas estimated to be about 1.29×10 ⁵ m·s ^-1,and the velocity of stepped leader of C-G lighting was about 1.73×10 ⁵ m·s ^-1.

• Spectral Properties of the Lightning Return Stroke
• YUAN Ping;LIU Xin-sheng;ZHANG Yi-jun;ZHANG Cui-hua;QIE Xiu-shu
• 2003 Vol. 22 (3): 235-238. 
• Abstract ( ) PDF (270KB) ( )
• The spectra in 390~660 nm regions from the first return strokes between cloud and ground have been obtained by a slit-less spectrograph.Appling the atomic structure theory to the research work on lightning spectra,wavelength,oscillator strengths and excited energy of upper levels have been calculated for the transitions of NII ions related to lightning discharges.Large-scale multi-configuration Dirac-Fock wave functions are applied to include the most important effects of relativity,correlation,and relaxation within the same(computational) model.Comparing with the calculated results of experimental spectra show that,during return stroke,the corresponding upper excited energies for most lines are around 23ev.NII is the most abundant ion among the channel plasma,and mainly in excited state of n=3.

• Measurement and Comparison of VHF/VLF Radiations of Preliminary Breakdown of Cloud-to-Ground and Intracloud Flashes
• ZHU Bao-you;MA Ming;TAO Shan-chang
• 2003 Vol. 22 (3): 239-245. 
• Abstract ( ) PDF (316KB) ( )
• The sequence of VLF bipolar radiation pulses and simultaneous VHF activitiesproduced by the preliminary breakdown of both cloud-to-ground(CG) flashes and intracloud(IC) flashes are presented.In the case of negative CG flashes,the sequence pulses tend to be of the same polarity as that of the succeeding return stroke,and their separating time average is about 160 μs.The duration of the whole sequence is about 2.2 ms on average.Unlike CG flashes,in the IC flashes from the same thunderstorm the preliminary breakdown is characterized by a positive large bipolar pulses sequence,lasting about 11.5 ms averagely with the pulse spacing time of about 1300 ms.The notable VHF radiation occurs almost at the same time as the onset of the VLF bipolar pulses sequences.The VLF bipolar pulses sequence accompanying by simultaneous VHF activities is the characteristic event during the preliminary breakdown of both CG flashes and IC flashes in Hefei area.During the preliminary breakdown of CG flashes VHF radiation envelope(bandwidth 100 kHz) appears in a quasi-continuous manner quite different from the intermittent VHF radiation during the initial breakdown of IC flashes.It is interesting to note that although VLF radiation and VHF emission during the initial breakdown are correlated in time,but they do not show an intensity-correlated tendency.Characteristics of VLF pulses sequences versus return strokes are also presented.The mean ratio between the amplitude of the largest pulse from the sequence and succeeding return stroke amplitude is about 0.43.For 105 cases the mean separation time between the first VLF pulse and the succeeding return strokes is 21 ms,while about 94% cases have their first VLF pulse appear within 40 ms before the onset of the first return stroke.

• The Influence of Channel Geometry on VLF/VHF Radiations from Lightning Return Strokes
• ZHU Bao-you;MA Ming;TAO Shan-chang
• 2003 Vol. 22 (3): 246-251. 
• Abstract ( ) PDF (263KB) ( )
• The change in propagation direction of the lightning current causedby the channel geometry(branch or tortuosity) may introduce subsidiary peaks into lightning return stroke waveformsand also alter its VHF radiation.By using the transmission-line-mode the influence of channel geometry on VLF/VHF radiation from lightning return strokes is presented.It is indicated that the strength of the subsidiary peak depends on the length and orientation of the channel geometry filaments.Among those heavily vertically-oriented filaments the large one(with the length of 100 m in scale) tends to produce subsidiary peak comparative to return strokes in strength and the small one(with the length of 1 m in scale or less) can only produce peaks weaker than 10% of return strokes,while the horizontally-oriented filament seems to produce no distinguishable subsidiary peaks.The average lengths of all channel branch or turtuosity filaments(ALF) are among the important channel geometry parameters and the intensity of the subsidiary peak and the interval time between successive peaks strongly relate to this parameter.In frequency domain the channel geometry can add to by a factor in maximum the high frequency energy of lightning return stroke radiation at the wavelength approximate 8 times ALF.However,this high frequency component is a factor weaker than the measured VHF radiation strength during lightning return strokes,strongly indicating that the channel branch or tortuosity is not the main source of VHF radiation from lightning return strokes.

• Reconstruction of Return Stroke Radiation Field Waveforms and Estimation of Cloud-to-Ground Discharges Parameters
• ZHANG Qi-lin;QIE Xiu-shu
• 2003 Vol. 22 (3): 252-258. 
• Abstract ( ) PDF (288KB) ( )
• Based on the traditional transmission line model,the relationship between the return stroke radiation field change and return stroke current pulse is rebuilt.According to the observed data,we reconstruct the electric field waveforms of return stroke in three different distance ranges(15~50 km,50~100 km,100~150 km),and estimate some parameters of cloud-to-ground discharges by a reasonable approximation.We find that the last leader pulse current before the first return stroke is 2.7 kA,the charge density in steppedleader channel is(0.135~1.35)×10 ^-3 C·m ^-1,the charge amount neutralized by the negative cloud-to-ground return stroke is 2.06 C.

• Optical and Electrical Characteristics of the Cloud-to-Ground Lightning Flash with Two-Striking-Point in the First Return-Stroke
• KONG Xiang-zhen;QIE Xiu-shu;WANG Cai-wei;ZHANG Yi-jun;WANG Huai-bin;ZHANG Cui-hua
• 2003 Vol. 22 (3): 259-267. 
• Abstract ( ) PDF (380KB) ( )
• Cloud-to-ground lightning flash with two-striking-point has been studied by using the simultaneous observation of the high-speed video camera system with 1000 frame s ^-1 resolution,slow and fast antenna systems with 1 μs time resolution.The time interval of the two channels reached at the ground is 30 μs.One of the leaders became an attempt leader just before the return-stroke R2.The M-components were found to be significantly brighter than the stepped leaders.The K-events were caused by intracloud breakdown and channel extension,which were usually accompanied by the luminescence within the cloud.In addition,the simultaneously optical and electrical observation confirmed that the speed of the dart-step leader was related to the time interval between it and the former return-stroke.The higher leader speed was associated with the shortertime interval between return strokes,and vice versa.Four possible causations were proposed for the formation of two-striking-point flash.

• Numerical Simulation of Different Charge Structures in Thunderstorm
• GUO Feng-xia;ZHANG Yi-Jun;QIE Xiu-shu;YAN Mu-hong
• 2003 Vol. 22 (3): 268-274. 
• Abstract ( ) PDF (311KB) ( )
• Using a three-dimensional dynamics-electrification,we do some simulation researchs on three parameters which determine the charge structure in thunderstorm.They are the reverse temperature,the most disturbance equivalent potential temperature in the center and disturbance region,respectively.The results indicate that the charge structure is different when we choose different parameter values.It can explain the reason why the thunderstorm of different regions,seasons and strengthshave different charge structures during the observation.

• Ground Observation of NO _x Generated by Lightning in Thunderstorm Weather
• ZHOU Yun-jun;QIE Xiu-shu;YAN Mu-hong;ZHANG Guang-shu
• 2003 Vol. 22 (3): 275-280. 
• Abstract ( ) PDF (296KB) ( )
• NO _x(NO+NO ₂) inducedby lightning is very important in the study on atmospheric chemistry.Actually,the observation of NO _xgenerated by lightning is rather difficult.In the paper,NO _x generated by the naturallightning,which was observed on the ground in Datong county of Qinghai province by utilizing NO _x analyzer,is analyzed.The results show as follows:Underfine weather stable condition,the average volume mixing ratio of NO _x is relatively stable.Although the observed value is higher than the one observed on the ground in the ideal clean background atmosphere,it is rather lower than the one obtained in the polluted air.In the process of thunderstorm weather,the number of lightningflashes is the same with the one of the peak values of the average volume mixing ratio of NO _x in the air,and the peak values are produced by lightning flashes.The energy difference of a single lightning in differentintensity thunderstorm weather is not more than 10 times.There are time lags between the peak values of volumemixing ratio of NO _x and lightning flashes.The order of the transportationtime of NO _x generated by lightning can be fitted by a quadratic,and the relative coefficientis rather high.There is not a strict linearity relationship between the transportation time and distance.The boundary value between high and low energy lightning flashes is 12~13×10 ⁶ J,thelightning flashes of high and low energy occurin alternation,and the time alternation increases with time passing.

• NO _x Actinic Flux Enhancement Inside Dirty Water Droplet
• YANG Wen
• 2003 Vol. 22 (3): 281-287. 
• Abstract ( ) PDF (305KB) ( )
• Based on the ray optics model of water droplet,a set of reflectance coefficient and meaningful refractive angle for the absorbing material are derived by a somewhat different treatments from previous one.The dirty cloud droplet polluted by highly absorbing inclusions can enhance the actinic flux,unless the absorptive coefficient very big.The results from effective medium approximations show that our actinic flux enhancement is larger than earlier ones.The values generally stay between 1.2~1.62.That is to say the droplet enhances the actinic flux by some 20% to 62%.In addition,the actinic flux enhancement factor will reduce as the absorptive coefficient and droplet radius increase.However,when the two impact parameters become very small this influence will get weaker and weaker.

• Lightning Activities on Qinghai-Xizang Plateau as Observed by Satellite Based Lightning Imaging Sensor
• QIE Xiu-shu;Ralf Toumi
• 2003 Vol. 22 (3): 288-294. 
• Abstract ( ) PDF (1099KB) ( )
• The lightning flash activities on Qinghai-Xizang Plateau are being studied,for the first time,by using Lightning Imaging Sensor(LIS) database.The flash activity is found to exhibit a continental type climate behavior and is a sensitive indicator of solar heating on the Plateau.Over 93% of the flashes are found to occur during May to September with a single peak in the summer.The monthly variation clearly shows a flash activity in May with the increase of surface heating and moisture.The high flash density on the Central Plateau reveals the affinity of lightning activity with the topography.The diurnal variation of the flash activity shows a peak activity from 14:00 to 18:00 LT with 63% of all flash activities occuring in this period.Less than 3% of all lightning flashes are observed between 00:00~10:00 LT.There is also a diurnal variation in the meanflash radiance with a sharp drop at around 02:00 LT,and increases rapidly from 08:00 LT with the sunrise.The optical radiance of flashes onthe Plateau can be fitted well to a lognormal distribution with energetic flashes on the Northern Plateau and weak flashes on the Western Plateau.The lower flash discharge energy on Qinghai-Xizang Plateau could be attibuted to the lower convective available potential energy and the lower cloud top.

• Analysis on Characteristics of Positive Cloud-to-Ground in Pingliang Area of Gansu
• ZHANG Yi-jun;YAN Mu-hong;ZHANG Cui-hua;WANG Huai-bin
• 2003 Vol. 22 (3): 295-300. 
• Abstract ( ) PDF (323KB) ( )
• The characteristics of positive cloud-to-ground(CG) in Pingliang area of Gansu province were analyzed by use of data of lightning location system and radar.The results indicated that the rise times of lightning return stroke were between 3~20 μs with 10.7 μs mean for positive CG and 8.33 μs for negative CG.The durations of return stroke were between 10~130 μs with 51 μs mean value for negative CG.While the durations of return stroke were between 10 μs~50 μs with 19.67 μs mean value for positive CG.The depth of the dip after the zero crossing was 32% for negative,and 55% for positive CG.The two peak values appeared in daily variation at 01:00 and 13:00 respectively for negative and only one peak value at 18:00 for positive CG lightning.The distribution was reverse correlation between positive and negative CG lightning.The time of hail was correspondingto that of the peak value of positive CG lightning.The occurrence of positive CG lightning was relation with the updraft and downdraft of solid hydrometeors in thunderstorm.

• Fast Recording System on Multi-Parameter of Lightning Flash with Sub-Microsecond Resolution
• ZHANG Guang-shu;QIE Xiu-shu;WANG Huai-bin;ZHANG Tong;CHEN Cheng-pin;ZHANG Yi-jun
• 2003 Vol. 22 (3): 301-305. 
• Abstract ( ) PDF (647KB) ( )
• This paper described how to record the slow and fast electric field changes produced by lightning flash with sub-microsecond time resolution in real time without data losing.The electric field from field mill was also recorded continuously in parallel.The replay of historical data was realized by using a data compressing method in several segments with same data length.The data from multi-task,with each in a working mode of multi-channel and huge data-capability,can be recorded automatically by pre-programming with VC++ in Win2000 platform.The absolute time accuracy of radiation pulses has reached 0.1 μs.Meanwhile,the recording speed is increased by 20 times faster than what we used before,and the measuring accuracy is also rose signifcantly.A bulk of data has been documented in the summer of 2002.It has been proved that the new recording system is reliable and stable,and it will be a powerful tool in the future lightning research.

• GPS-Based Multi-Station Synchronized System of Lightning Electric-Magnetic Radiation
• ZHANG Tong;ZHANG Guang-shu;QIE Xiu-shu
• 2003 Vol. 22 (3): 306-310. 
• Abstract ( ) PDF (238KB) ( )
• By use of GPS(Global Positioning System) of PPS(Pulse Per Second) and precise timing circuit,multi-station to measure lighting electric-magnetic radiation pulse is synchronized.The error of precise timing circuit caused by crystal oscillator frequency excursion is also solved.The synchronizing precision can be 50 ns.In this paper,the synchronizing system data obtained in the field experiment is described.The reliability of this system is also verified.

• The Triggering Device for Synchronizing Record of Parameters of Lightning Discharge
• ZHANG Guang-shu;ZHANG Tong;QIE Xiu-shu;CHEN Cheng-pin
• 2003 Vol. 22 (3): 311-314. 
• Abstract ( ) PDF (186KB) ( )
• The transient analog signal of lightning discharge is captured,which selected by a window level for pre-triggering,a pulse signal with a width of 100 μs and 10 ns positive slope of certain amplitude is generated.It can be used to trigger the observing instruments of lightning and precise clocks synchronized by GPS at the same time.The start point of recording can be fixed in the waveform generated by lightning discharge.The time of absolute recording precision is decided by the highly precise clock.So the different parameters of lightning discharge can be recorded at the same starting moment.A highly accurate time base is provided for analyzing the high resolution of parameters of lightning and the time difference of arrival at different observing sites.