【作者】 师正；

【导师】 谭涌波；

【作者基本信息】 南京信息工程大学 ， 雷电科学与技术， 2012， 硕士

【摘要】 本文的主要工作是在已有的放电参数化方案的基础上,通过改变模式中的初始扰动对四次雷暴进行了多次二维12.5m分辨率放电模拟实验,再现了多种雷暴云电荷结构下的地闪放电现象,就空间电环境特征与地闪接地点之间的相互关系进行了分析,并对三极性雷暴云底部正电荷对闪电放电的影响程度进行了定量估计以及合理性评价；此外,通过建立雷暴云电荷结构模型进行放电模拟实验,分析了雷暴云电荷分布与闪电通道扩展范围的相互关系,并揭示了在具有不同云内电荷浓度分布特征的雷暴云电荷结构下,云闪放电的分形特征以及存在的差异。主要研究成果如下：(1)三极性雷暴云底部正电荷的大小与分布范围对闪电的放电具有显著影响。在产生负地闪的三极性雷暴云中,底部正电荷缩小至一定量级时,闪电停止发生；而放大一定量级后形成了一种云内反极性放电过程；在产生云闪的三极性雷暴云中,底部正电荷的范围扩大后能产生反极性云闪；在产生正地闪的三极性雷暴云中,底部正电荷对下行正先导具有同性排次作用,其中底部次生正电荷堆电荷量越大和水平分布范围越宽,对下行正先导的抑制作用越明显。(2)闪电传播的随机性所带来的地闪击地点的不确定范围被限制在3km之内,利用动态聚类法迭代得出的三个击地点位置之间的差为1km左右。负地闪的初始点与击地点的位置差主要分布在0～6km范围内,正、负地闪主要产生于离地面最近的一对电荷堆之间,其起始高度越高,初始点与击地点位置差分布越广；产生于三级性雷暴云电荷结构下的正地闪,其初始于上部的主正电荷堆与中部主负电荷堆之间,其击地点与初始点的距离基本在6km以上。(3)闪电先导传播范围与电荷堆尺度保持正相关性。云闪通道在穿过电荷累积区中心以前,有较好的分形特征,幂指数约为1.757。云内高密度电荷中心附近电荷浓度变化缓慢,会导致幂指数增加。更多还原

【Abstract】 This paper use an existing stochastic lightning model and four souding data to perform a2-dimensional thunderstorms numerical simulation experiment which resolution is12.5m. Gives ground flash cases base on different thunderstorm cloud charge structure, and analyzes the relationship between characteristics of electrical environment and ground stroke point. Quantitative estimated the influence of positive charge pile in the bottom of a3-poled thunderstorm on lightning discharge and give rationality evaluated; what’s more, makes discharge simulation experiment through establishing space structure model of thunderstorm cloud charge, besides, analysis the relationships between the space charge distribution of thunderstorm and lightning channel extended range, reveals the difference of lightning fractal characteristics under different charge concentration distribution in thunder cloud. The main research results are as follows:1) Under a3-poled thunderstorm which can generate Negative CG lightning,The size and distribution of positive charge pile in the bottom of a3-poled thunderstorm has significant influence on lightning discharge.; when the bottom positive charge pile is narrowed a certain grade, Lightning will cease; when the bottom positive pile is enlarged a certain magnitude, Reverse polarity of cloud flashes will occur. In a3-poled thunderstorm which can generate IC lightning, when the range of positive charge pile in the bottom is enlarged. Reverse polarity of cloud flashes may occur. In a3-poled thunderstorm which can generate Positive CG lightning, the bottom positive charge pile will exclude the downlink leader, because they have charges of the same polarity. The larger of the quantity and distribution range of charge, The stronger of impact of the bottom positive pile on the downlink leader.2) Ground strike point uncertainty range is limited to3km because of the lightning propagation randomness, Using dynamic clustering method to iterative three locations which differ about1km. The distance between the initial point and ground strike point of negative CG lightning is mainly distributed in the range of0～6km; CG lightning primarily is produced in a pair of charges which close to ground, the higher of lightning starting height, the larger of range of distance between the initial point and ground strike point; some positive CG lightning which are produced in the three stage of charge structure of thunderstorm cloud is initial between upper part of positive charge pile and mid negative charge pile, the distance between the initial point and ground strike point is basically above6km.3) The range of Lightning leader propagates keeps positive correlation with the scale of charge in thunderstorm cloud. Before the channel of IC lightning through the charge accumulation centers, lightning The channel of IC lightning have fractal characteristics, the exponent is about1.757, If charge density changes slowly in some place where near the area of high-density charge, exponential will increase.更多还原