[Objective] The study aims to analyze characteristics of thunderstorm activity in Hefei City. [Method] Based on conventional ground observational data during1981-2010 and lightning location data in 2010-2013 in Hefei ...[Objective] The study aims to analyze characteristics of thunderstorm activity in Hefei City. [Method] Based on conventional ground observational data during1981-2010 and lightning location data in 2010-2013 in Hefei City, temporal and spatial variation of thunderstorm days were analyzed using statistical methods, and then the distribution laws of thunderstorm days were compared with the lightning location data. [Result] In Hefei City, multi-year average of thunderstorm days from1981 to 2010 was more in the south but less in the north, and annual distribution of thunderstorm days was extremely uneven. Moreover, there were obvious seasonal and monthly variation in thunderstorm days in Hefei City. Thunderstorm days were the most in summer, and monthly average of thunderstorm days in Hefei City had a peak in July. From 2010 to 2013, the monthly variation curves of total frequency of cloud-to-ground lightning and frequency of negative cloud-to-ground lightning in Hefei City had a peak each, and cloud-to-ground lightning was frequent in July and August, especially August. The frequency of cloud-to-ground lightning exceeded the average from 12：00 to 21：00. The maximum intensity of cloud-to-ground lightning in Hefei City varied greatly in different months, and it was the highest in July. There are certain differences between the two kinds of data in the distribution laws, so it is needed to combine data of lightning position indicator and long-term artificial observation data to study the detection efficiency of lightning position indicator. [Conclusion] The research can provide theoretical references for lightning protection and disaster reduction in Hefei City.展开更多
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 o...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.展开更多
The authors report the observation of Extremely Low Frequency （ELF） plasma turbulence registered by DEMETER satellite in the ionosphere over the seismic and thunderstorm areas. The detail analysis of the electric fi...The authors report the observation of Extremely Low Frequency （ELF） plasma turbulence registered by DEMETER satellite in the ionosphere over the seismic and thunderstorm areas. The detail analysis of the electric field fluctuations for the selected strong earthquakes and thunderstorm is presented. Special attention is given to study of the characteristics of the spectra of these variations and searches of the nonlinear effects. This analysis is possible in the time interval when the waveform has been transmitted. Some attempt of this discussion is given in the paper.展开更多
Combined with the existing stochastic lightning parameterization scheme, a classic tripole charge structure in thunderstorms is assumed in the paper, and then 2-dimensional fine-resolution lighting discharge simulatio...Combined with the existing stochastic lightning parameterization scheme, a classic tripole charge structure in thunderstorms is assumed in the paper, and then 2-dimensional fine-resolution lighting discharge simulations are performed to quantitatively investigate the effect of lower positive charge(LPC) on different types of lightning. The results show:(1) The LPC plays a key role in generating negative cloud-to-ground(CG) flashes and inverted intra-cloud(IC) lightning, and with the increase of charge density or distribution range of LPC region, lightning type changes from positive polarity IC lightning to negative CG flashes and then to inverted IC lightning.(2) Relative to distribution range of charge regions, the magnitude of charge density of the LPC region plays a dominant role in lightning type. Only when the maximal charge density value of LPC region is within a certain range, can negative CG flashes occur, and the occurrence probability is relatively fixed.(3) In this range, the charge density and distribution range of LPC region jointly determine the occurrence of negative CG flashes, which has a linear boundary with the trigger condition of IC lightning.(4) The common effect of charge density and distribution range of the LPC region is to change the distribution of positive potential well of bottom part of thunderstorms, and inverted IC lightning occurs when the initial reference potential is close to 0 MV, and negative CG flashes occur when the initial reference potential is far less than 0 MV.展开更多
Here we report characteristics of more than 100 cases of Narrow Bipolar Events(NBEs)occurred during two thunderstorms on the basis of our analysis of the dataset collected by a GPS based three-station time of arrival(...Here we report characteristics of more than 100 cases of Narrow Bipolar Events(NBEs)occurred during two thunderstorms on the basis of our analysis of the dataset collected by a GPS based three-station time of arrival(TOA)lightning location system deployed in Northeast China during the summer of 2010.All of the NBEs were of positive polarity and the amplitude of VLF/LF initial pulse of NBE was comparable to that of return strokes.The waveform characteristics of 166 NBEs that occurred within 150 km were consistent with the results of other reports.The average value of initial peak width of the bipolar pulse is 7.8±1.5 μs,full width at half maximum is 4.6±1.0 μs,and the ratio of initial peak amplitude to overshoot peak is 2.1±0.6.The inferred source height of NBEs occurred in two thunderstorms averaged 9.6 and 7.4 km above mean sea level,whereas the corresponding virtual ionosphere heights at two different times were 89 and 78 km,respectively.In NBEproducing thunderstorms,NBEs tended to burst during the active stage of normal lightning;nevertheless,no determinate quantitative relations could be established between them.In Storm 0711,NBEs were inclined to cluster at the proximity of particular convective cores with high radar reflectivity,and NBEs tended to move consistently at the front area of those NBE-producing convective cores during the evolution of thunderstorm.展开更多
文摘[Objective] The study aims to analyze characteristics of thunderstorm activity in Hefei City. [Method] Based on conventional ground observational data during1981-2010 and lightning location data in 2010-2013 in Hefei City, temporal and spatial variation of thunderstorm days were analyzed using statistical methods, and then the distribution laws of thunderstorm days were compared with the lightning location data. [Result] In Hefei City, multi-year average of thunderstorm days from1981 to 2010 was more in the south but less in the north, and annual distribution of thunderstorm days was extremely uneven. Moreover, there were obvious seasonal and monthly variation in thunderstorm days in Hefei City. Thunderstorm days were the most in summer, and monthly average of thunderstorm days in Hefei City had a peak in July. From 2010 to 2013, the monthly variation curves of total frequency of cloud-to-ground lightning and frequency of negative cloud-to-ground lightning in Hefei City had a peak each, and cloud-to-ground lightning was frequent in July and August, especially August. The frequency of cloud-to-ground lightning exceeded the average from 12：00 to 21：00. The maximum intensity of cloud-to-ground lightning in Hefei City varied greatly in different months, and it was the highest in July. There are certain differences between the two kinds of data in the distribution laws, so it is needed to combine data of lightning position indicator and long-term artificial observation data to study the detection efficiency of lightning position indicator. [Conclusion] The research can provide theoretical references for lightning protection and disaster reduction in Hefei City.
基金supported by the China Meteorological Administration (Grant No. GYHY201406002)the Key Program of the Chinese Academy of Sciences (Grant No. 2013CB430100)
文摘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.
文摘The authors report the observation of Extremely Low Frequency （ELF） plasma turbulence registered by DEMETER satellite in the ionosphere over the seismic and thunderstorm areas. The detail analysis of the electric field fluctuations for the selected strong earthquakes and thunderstorm is presented. Special attention is given to study of the characteristics of the spectra of these variations and searches of the nonlinear effects. This analysis is possible in the time interval when the waveform has been transmitted. Some attempt of this discussion is given in the paper.
基金supported by the National Basic Research Program of China(Grant No.2014CB441403)the National Natural Science Foundation of China(Grant No.41175003)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Combined with the existing stochastic lightning parameterization scheme, a classic tripole charge structure in thunderstorms is assumed in the paper, and then 2-dimensional fine-resolution lighting discharge simulations are performed to quantitatively investigate the effect of lower positive charge(LPC) on different types of lightning. The results show:(1) The LPC plays a key role in generating negative cloud-to-ground(CG) flashes and inverted intra-cloud(IC) lightning, and with the increase of charge density or distribution range of LPC region, lightning type changes from positive polarity IC lightning to negative CG flashes and then to inverted IC lightning.(2) Relative to distribution range of charge regions, the magnitude of charge density of the LPC region plays a dominant role in lightning type. Only when the maximal charge density value of LPC region is within a certain range, can negative CG flashes occur, and the occurrence probability is relatively fixed.(3) In this range, the charge density and distribution range of LPC region jointly determine the occurrence of negative CG flashes, which has a linear boundary with the trigger condition of IC lightning.(4) The common effect of charge density and distribution range of the LPC region is to change the distribution of positive potential well of bottom part of thunderstorms, and inverted IC lightning occurs when the initial reference potential is close to 0 MV, and negative CG flashes occur when the initial reference potential is far less than 0 MV.
基金supported by the R&D Special Fund for Public Welfare Industry(Grant GYHY:(forestry) 200704027 and (meteorology) GYHY201006005)National Natural Science Foundation of China (Grant Nos. 41075001 and 40775003)
文摘Here we report characteristics of more than 100 cases of Narrow Bipolar Events(NBEs)occurred during two thunderstorms on the basis of our analysis of the dataset collected by a GPS based three-station time of arrival(TOA)lightning location system deployed in Northeast China during the summer of 2010.All of the NBEs were of positive polarity and the amplitude of VLF/LF initial pulse of NBE was comparable to that of return strokes.The waveform characteristics of 166 NBEs that occurred within 150 km were consistent with the results of other reports.The average value of initial peak width of the bipolar pulse is 7.8±1.5 μs,full width at half maximum is 4.6±1.0 μs,and the ratio of initial peak amplitude to overshoot peak is 2.1±0.6.The inferred source height of NBEs occurred in two thunderstorms averaged 9.6 and 7.4 km above mean sea level,whereas the corresponding virtual ionosphere heights at two different times were 89 and 78 km,respectively.In NBEproducing thunderstorms,NBEs tended to burst during the active stage of normal lightning;nevertheless,no determinate quantitative relations could be established between them.In Storm 0711,NBEs were inclined to cluster at the proximity of particular convective cores with high radar reflectivity,and NBEs tended to move consistently at the front area of those NBE-producing convective cores during the evolution of thunderstorm.
