Using the spatial coordinates of detection stations and the time of arrival of lightning wave, the observation equations can be expressed. For the large lightning detection network, the least square method is used to ...Using the spatial coordinates of detection stations and the time of arrival of lightning wave, the observation equations can be expressed. For the large lightning detection network, the least square method is used to process the adjustment of observation data to find the most probable value of lightning position, and the result is assessed by the mean error and dilution of precision. Lightning location precision is affected by figure factor. The conclusion can be used in the design of location network, data processing, and data analysis.展开更多
Observations show that the sequences of microsecond-scale pulses are produced in cloud flash discharge processes.In the present work we report on measurements of larger bipolar pulses (LBP)of the radiation fields whic...Observations show that the sequences of microsecond-scale pulses are produced in cloud flash discharge processes.In the present work we report on measurements of larger bipolar pulses (LBP)of the radiation fields which are classified into four types according to their waveshapes and polarities of initial peak.Either positive or negative pulse contains two kinds of waveshapes:one with a smooth rise and the other with 2 or 3 fast-rising pulse superimposed on the initial half cycle. The pulse waveshape characteristics in both time and frequency domains are as follows.Among 2908 samples there are 45% of the positive polarity and 55% of the negative polarity.The positive pulses tend to have distinctly smaller values than negative pulses in rise time,half width and zero- crossing time of the initial peak.The peaks of positive pulse spectra tend to occur at a higher frequency than those of negative pulses.Despite differences above,positive and negative pulses have a similar total duration.展开更多
Based on the transmission line equations, this paper has developed computing formulas of current and voltage induced on the cable over the ground plane by Flash of Lightning Between Clouds (FBC), and estimated current...Based on the transmission line equations, this paper has developed computing formulas of current and voltage induced on the cable over the ground plane by Flash of Lightning Between Clouds (FBC), and estimated current and voltage on the cable of metal shielded sheath and analyzed the results.展开更多
Based on the relationship between lightning flash density and radar echoes and a statistical analysis using satellite and radar observations,a scheme was introduced into the mesoscale model GRAPES（Global and Regional...Based on the relationship between lightning flash density and radar echoes and a statistical analysis using satellite and radar observations,a scheme was introduced into the mesoscale model GRAPES（Global and Regional Assimilation and PrEdiction System）to forecast the cloud to ground（CC）flash activities.Because the relationship is a necessary but not sufficient condition for lightning,an additional constraint condition related to temperature of cloud top is added into the scheme to determine whether the lightning activity really occurs.Only if the lightning activity meets the criterion to occur,the CG flash density in a grid is considered to be valid.This was proved to be necessary for reducing the false prediction.Two cases that occurred on the edge of the subtropical high in coastal regions of South China were simulated to examine the efficiency of the scheme.The results showed that the scheme was capable of forecasting lightning activities in South China.The simulated lightning areas agreed with the CG flash observations,and the CG flash density forecast by the model was also consistent with observational results in magnitude.In consideration of the forecast aging of the explicit cloud microphysical scheme in GRAPES,lightning activities can now be forecast accurately within 6 h.展开更多
基金Supported by the National Key Technologies R&D Program of China (2008BAC36B00)
文摘Using the spatial coordinates of detection stations and the time of arrival of lightning wave, the observation equations can be expressed. For the large lightning detection network, the least square method is used to process the adjustment of observation data to find the most probable value of lightning position, and the result is assessed by the mean error and dilution of precision. Lightning location precision is affected by figure factor. The conclusion can be used in the design of location network, data processing, and data analysis.
基金the National Natural Science Foundation of China.
文摘Observations show that the sequences of microsecond-scale pulses are produced in cloud flash discharge processes.In the present work we report on measurements of larger bipolar pulses (LBP)of the radiation fields which are classified into four types according to their waveshapes and polarities of initial peak.Either positive or negative pulse contains two kinds of waveshapes:one with a smooth rise and the other with 2 or 3 fast-rising pulse superimposed on the initial half cycle. The pulse waveshape characteristics in both time and frequency domains are as follows.Among 2908 samples there are 45% of the positive polarity and 55% of the negative polarity.The positive pulses tend to have distinctly smaller values than negative pulses in rise time,half width and zero- crossing time of the initial peak.The peaks of positive pulse spectra tend to occur at a higher frequency than those of negative pulses.Despite differences above,positive and negative pulses have a similar total duration.
文摘Based on the transmission line equations, this paper has developed computing formulas of current and voltage induced on the cable over the ground plane by Flash of Lightning Between Clouds (FBC), and estimated current and voltage on the cable of metal shielded sheath and analyzed the results.
基金Supported by the National Science & Technology Pillar Program of Ministry of Finance under Grant No.2008BAC36B04the National Natural Science Foundation of China under Grant No.40875003the Basic Scientific Research and Operation Fund of Chinese Academy of Meteorological Sciences under Grant No.2008Y003
文摘Based on the relationship between lightning flash density and radar echoes and a statistical analysis using satellite and radar observations,a scheme was introduced into the mesoscale model GRAPES（Global and Regional Assimilation and PrEdiction System）to forecast the cloud to ground（CC）flash activities.Because the relationship is a necessary but not sufficient condition for lightning,an additional constraint condition related to temperature of cloud top is added into the scheme to determine whether the lightning activity really occurs.Only if the lightning activity meets the criterion to occur,the CG flash density in a grid is considered to be valid.This was proved to be necessary for reducing the false prediction.Two cases that occurred on the edge of the subtropical high in coastal regions of South China were simulated to examine the efficiency of the scheme.The results showed that the scheme was capable of forecasting lightning activities in South China.The simulated lightning areas agreed with the CG flash observations,and the CG flash density forecast by the model was also consistent with observational results in magnitude.In consideration of the forecast aging of the explicit cloud microphysical scheme in GRAPES,lightning activities can now be forecast accurately within 6 h.
