为揭示北京地区闪电气候特征,笔者选取2009—2016年该地区ADTD探测资料,对闪电参数特征进行统计分析,包括时间分布、闪电强度、雷电流幅值累积概率等。结果表明:该地区2009—2016年间共发生闪电155567次,负闪和正闪分别占90.0%和10.0%,...为揭示北京地区闪电气候特征,笔者选取2009—2016年该地区ADTD探测资料,对闪电参数特征进行统计分析,包括时间分布、闪电强度、雷电流幅值累积概率等。结果表明:该地区2009—2016年间共发生闪电155567次,负闪和正闪分别占90.0%和10.0%,前期和后期相比,总闪频次降幅接近30.0%,但正闪频次增幅高于36.1%。夏季是北京地区闪电的高发季节,占全年闪电数量的82.1%左右,和该地区主汛期有较好的对应关系。该地区负闪电流强度分布比较集中,而正闪电流强度分布相对分散,平均强度为-33.9 k A和63.5 k A,与历史统计结果相比均有所增强。利用IEEE工作组推荐的累积概率分布函数,更能客观反映该地区雷电流幅值分布特征,拟合曲线的决定系数高于0.99。展开更多
本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、...本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、雹与云滴之间的感应起电机制。放电参数化方案只考虑了闪电的整体效应。对一次超级单体的模拟结果表明,电荷结构呈现正、负、正的三极性结构,主正电荷区在-40℃到-60℃之间,主负电荷区在-10℃到-30℃之间,下部正电荷区在零度层附近,总电荷浓度最大值接近2nC/m3。这种电荷结构的垂直分布同以往在强对流天气系统中观测到的典型电荷结构一致。对飑线过程的模拟结果表明,部分单体电荷结构呈现出反的偶极性且飑线中最大电荷浓度小于超级单体。在飑线成熟阶段,模拟得到的闪电分布与观测的地闪活动在分布型上相似。展开更多
One function for approximating pulse quantities in high voltage technique is presented in this paper. The function derivative, its integral, as well as its Laplace and Fourier transform are obtained analytically. Inte...One function for approximating pulse quantities in high voltage technique is presented in this paper. The function derivative, its integral, as well as its Laplace and Fourier transform are obtained analytically. Integral transformations of the pulse function are needed in frequency domain calculations of lightning induced effects in the case of a lossy ground. The pulse function having adequately chosen parameters is applied in lightning discharge modeling for lightning electromagnetic field calculation, and the results are in agreement with the results from literature. The choice of function parameters is based on their influence on the pulse waveshape which is presented in the paper. Numerical results for the Fourier transform are presented for different usually used pulse functions. The advantages of this function are simple choice of its parameters according to the desired waveshape characteristics and analytical solutions useful in lightning discharge modeling, electromagnetic field computation and induced effects calculations.展开更多
The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding...The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground(CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs(OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning(IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL(STUL) is initiated mainly during the dissipation stage of a thunderstorm.展开更多
文摘为揭示北京地区闪电气候特征,笔者选取2009—2016年该地区ADTD探测资料,对闪电参数特征进行统计分析,包括时间分布、闪电强度、雷电流幅值累积概率等。结果表明:该地区2009—2016年间共发生闪电155567次,负闪和正闪分别占90.0%和10.0%,前期和后期相比,总闪频次降幅接近30.0%,但正闪频次增幅高于36.1%。夏季是北京地区闪电的高发季节,占全年闪电数量的82.1%左右,和该地区主汛期有较好的对应关系。该地区负闪电流强度分布比较集中,而正闪电流强度分布相对分散,平均强度为-33.9 k A和63.5 k A,与历史统计结果相比均有所增强。利用IEEE工作组推荐的累积概率分布函数,更能客观反映该地区雷电流幅值分布特征,拟合曲线的决定系数高于0.99。
文摘本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、雹与云滴之间的感应起电机制。放电参数化方案只考虑了闪电的整体效应。对一次超级单体的模拟结果表明,电荷结构呈现正、负、正的三极性结构,主正电荷区在-40℃到-60℃之间,主负电荷区在-10℃到-30℃之间,下部正电荷区在零度层附近,总电荷浓度最大值接近2nC/m3。这种电荷结构的垂直分布同以往在强对流天气系统中观测到的典型电荷结构一致。对飑线过程的模拟结果表明,部分单体电荷结构呈现出反的偶极性且飑线中最大电荷浓度小于超级单体。在飑线成熟阶段,模拟得到的闪电分布与观测的地闪活动在分布型上相似。
文摘One function for approximating pulse quantities in high voltage technique is presented in this paper. The function derivative, its integral, as well as its Laplace and Fourier transform are obtained analytically. Integral transformations of the pulse function are needed in frequency domain calculations of lightning induced effects in the case of a lossy ground. The pulse function having adequately chosen parameters is applied in lightning discharge modeling for lightning electromagnetic field calculation, and the results are in agreement with the results from literature. The choice of function parameters is based on their influence on the pulse waveshape which is presented in the paper. Numerical results for the Fourier transform are presented for different usually used pulse functions. The advantages of this function are simple choice of its parameters according to the desired waveshape characteristics and analytical solutions useful in lightning discharge modeling, electromagnetic field computation and induced effects calculations.
基金supported by the National Key Basic Research Development Program of China (Grant No. 2014CB441403)the National Natural Science Foundation of China (Grant Nos. 41175003 & 41475003)
文摘The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground(CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs(OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning(IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL(STUL) is initiated mainly during the dissipation stage of a thunderstorm.
