We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The ...We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.展开更多
“双碳”战略和“交通强国”战略使得轨道交通系统向着高效能、高弹性和绿色化的方向发展。轨道交通系统自身具有丰富的资源,通过在其路域铺设新能源,并根据需要配置储能,构建轨道交通自洽能源系统,可实现系统的资产能源化,助力系统向...“双碳”战略和“交通强国”战略使得轨道交通系统向着高效能、高弹性和绿色化的方向发展。轨道交通系统自身具有丰富的资源,通过在其路域铺设新能源,并根据需要配置储能,构建轨道交通自洽能源系统,可实现系统的资产能源化,助力系统向绿色化方向演进。但随机性轨道交通负荷与随机性新能源出力相交织,使得轨道交通自洽能源系统的规划配置面临难题。为此,该文构建了轨道交通路域风力、光伏以及牵引负荷的不确定集合,从而考虑了供需双向不确定性;在此基础上,以年均成本最小为目标函数,并针对牵引变压器等自洽能源系统的组分进行分析,形成系统内各组分应满足的约束条件,从而构建了适应轨道交通运行需求的新能源-储能规划配置两阶段鲁棒优化模型;针对该模型的特点,采用改进列和约束生成(improved column and constraint generation,IC&CG)算法予以求解。算例分析结果表明,所提出的模型可以使得系统的自洽率满足设定要求,并降低了系统的碳排放成本,对推进轨道交通绿色化具有积极的推动作用。展开更多
Data from the Beijing SAFIR 3000 lightning detection system and Doppler radar provided some insights into the three-dimensional lightning structure and evolution of a leading-line and trailing-stratiform （LLTS） meso...Data from the Beijing SAFIR 3000 lightning detection system and Doppler radar provided some insights into the three-dimensional lightning structure and evolution of a leading-line and trailing-stratiform （LLTS） mesoscale convective system （MCS） over Beijing on 31 July 2007. Most of the lightning in the LLTS-MCS was intracloud （IC） lightning, while the mean ratio of positive cloud-to-ground （＋CG） lightning to –CG lightning was 1：4, which was higher than the average value from previous studies. The majority of CG lightning occurred in the convective region of the radar echo, particularly at the leading edge of the front. Little IC lightning and little ＋CG lightning occurred in the stratiform region. The distribution of the CG lightning indicated that the storm had a tilted dipole structure given the wind shear or the tripole charge structure. During the storm’s development, most of the IC lightning occurred at an altitude of ～9.5 km; the lightning rate reached its maximum at 10.5 km, the altitude of IC lightning in the mature stage of the storm. When the thunderstorm began to dissipate, the altitude of the IC lightning decreased gradually. The spatial distribution of lightning was well correlated with the rainfall on the ground, although the peak value of rainfall appeared 75 min later than the peak lightning rate.展开更多
The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） f...The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） flashes and Cloud-to-Ground （CG） flashes, and the ADTD （ADvanced TOA and Direction system; TOA denotes time of arrival） network of China for CG lightning. Fourteen isolated hail-bearing thunderstorms in this region were examined in this study, using the data of SAFIR and ADTD. The peak of lightning frequency, for both total lightning and CG lightning, was often observed in advance of the occurrence of hailstones on the ground, with a trend of a rapid increase of lightning frequency before the hail was reported. The average lead times of the two types of lightning jump before hail events were obtained （total lightning： 32.2 min; CG： 25.4 min） through the 2a lightning jump algorithm. Additionally, in hailstorms with a high ratio of positive CG flashes, the diameter of hail was larger and the duration of hail was longer; when negative CG flashes dominated, the diameter of hail was relatively small. The comparison of the characteristics of total lightning and CG flashes in hailstorms in this study is expected to serve as a supplementary tool for hail forecasting.展开更多
By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial ...By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial and temporal characteristics of CG lightning flashes in 10 severe hailstorms are analyzed. The results show that the percentage of +CG lightning in these hailstorms is high with an average value of 45.5%. There is a distinct increase in CG flash rate during the rapid development stage of hailstorms. The hailstone falling corresponds to an active positive flash period, and the increase of +CG flash rate is generally accompanied with a decrease of –CG flash rate. The flash rate declines rapidly during the dissipating stage of hailstorms. The precipitation structure and lightning activity in two typical hail- storms are studied in detail. It is found that strong convective cells with reflectivity greater than 30dBZ mainly are situated in the front region of hailstorms, whereas the trailing stratiform region is in the rear part of the hailstorms. The maximum heights of echo top are higher than 14 km. Convective rain con- tributes much more rainfall to the total than stratiform rain, and the convective rain takes about 85% and 97% of the total in the two cases, respectively. Total lightning in the hailstorms is very active with the flash rate up to 183 fl/min and 55 fl/min, respectively. The results also indicate that most lightning flashes occurred in the echo region greater than 30 dBZ and its immediate periphery. The probability of lightning occurrence is 20 times higher in the convective region than in the stratiform region. The result suggests that the lightning information is helpful to the identification of convective rain region. The linear relationship between flash rate and ice water content is disclosed primarily.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
文摘We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.
文摘“双碳”战略和“交通强国”战略使得轨道交通系统向着高效能、高弹性和绿色化的方向发展。轨道交通系统自身具有丰富的资源,通过在其路域铺设新能源,并根据需要配置储能,构建轨道交通自洽能源系统,可实现系统的资产能源化,助力系统向绿色化方向演进。但随机性轨道交通负荷与随机性新能源出力相交织,使得轨道交通自洽能源系统的规划配置面临难题。为此,该文构建了轨道交通路域风力、光伏以及牵引负荷的不确定集合,从而考虑了供需双向不确定性;在此基础上,以年均成本最小为目标函数,并针对牵引变压器等自洽能源系统的组分进行分析,形成系统内各组分应满足的约束条件,从而构建了适应轨道交通运行需求的新能源-储能规划配置两阶段鲁棒优化模型;针对该模型的特点,采用改进列和约束生成(improved column and constraint generation,IC&CG)算法予以求解。算例分析结果表明,所提出的模型可以使得系统的自洽率满足设定要求,并降低了系统的碳排放成本,对推进轨道交通绿色化具有积极的推动作用。
基金supported by the National Natural Science Foundation of China(Grant No. 40930949)Key Subject Project of Beijing Atmospheric Physics and Environment,the One Hundred Person Project of the Chinese Academy of Sciences
文摘Data from the Beijing SAFIR 3000 lightning detection system and Doppler radar provided some insights into the three-dimensional lightning structure and evolution of a leading-line and trailing-stratiform （LLTS） mesoscale convective system （MCS） over Beijing on 31 July 2007. Most of the lightning in the LLTS-MCS was intracloud （IC） lightning, while the mean ratio of positive cloud-to-ground （＋CG） lightning to –CG lightning was 1：4, which was higher than the average value from previous studies. The majority of CG lightning occurred in the convective region of the radar echo, particularly at the leading edge of the front. Little IC lightning and little ＋CG lightning occurred in the stratiform region. The distribution of the CG lightning indicated that the storm had a tilted dipole structure given the wind shear or the tripole charge structure. During the storm’s development, most of the IC lightning occurred at an altitude of ～9.5 km; the lightning rate reached its maximum at 10.5 km, the altitude of IC lightning in the mature stage of the storm. When the thunderstorm began to dissipate, the altitude of the IC lightning decreased gradually. The spatial distribution of lightning was well correlated with the rainfall on the ground, although the peak value of rainfall appeared 75 min later than the peak lightning rate.
基金Supported by the National Natural Science Foundation of China (41030960 and 41105122)Project for Integration and Application of Meteorological Key Technology by the China Meteorological Administration (CAMGJ2012M78)National Science and Technology Support Program of China (2008BAC36B04)
文摘The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） flashes and Cloud-to-Ground （CG） flashes, and the ADTD （ADvanced TOA and Direction system; TOA denotes time of arrival） network of China for CG lightning. Fourteen isolated hail-bearing thunderstorms in this region were examined in this study, using the data of SAFIR and ADTD. The peak of lightning frequency, for both total lightning and CG lightning, was often observed in advance of the occurrence of hailstones on the ground, with a trend of a rapid increase of lightning frequency before the hail was reported. The average lead times of the two types of lightning jump before hail events were obtained （total lightning： 32.2 min; CG： 25.4 min） through the 2a lightning jump algorithm. Additionally, in hailstorms with a high ratio of positive CG flashes, the diameter of hail was larger and the duration of hail was longer; when negative CG flashes dominated, the diameter of hail was relatively small. The comparison of the characteristics of total lightning and CG flashes in hailstorms in this study is expected to serve as a supplementary tool for hail forecasting.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40325013, 40505001 and 40135010)
文摘By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial and temporal characteristics of CG lightning flashes in 10 severe hailstorms are analyzed. The results show that the percentage of +CG lightning in these hailstorms is high with an average value of 45.5%. There is a distinct increase in CG flash rate during the rapid development stage of hailstorms. The hailstone falling corresponds to an active positive flash period, and the increase of +CG flash rate is generally accompanied with a decrease of –CG flash rate. The flash rate declines rapidly during the dissipating stage of hailstorms. The precipitation structure and lightning activity in two typical hail- storms are studied in detail. It is found that strong convective cells with reflectivity greater than 30dBZ mainly are situated in the front region of hailstorms, whereas the trailing stratiform region is in the rear part of the hailstorms. The maximum heights of echo top are higher than 14 km. Convective rain con- tributes much more rainfall to the total than stratiform rain, and the convective rain takes about 85% and 97% of the total in the two cases, respectively. Total lightning in the hailstorms is very active with the flash rate up to 183 fl/min and 55 fl/min, respectively. The results also indicate that most lightning flashes occurred in the echo region greater than 30 dBZ and its immediate periphery. The probability of lightning occurrence is 20 times higher in the convective region than in the stratiform region. The result suggests that the lightning information is helpful to the identification of convective rain region. The linear relationship between flash rate and ice water content is disclosed primarily.
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.
