| 闪电初始阶段和尺度判别方法及其特征 |
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| 引用本文： | 张志孝,郑栋,张义军,陆高鹏.闪电初始阶段和尺度判别方法及其特征[J].应用气象学报,2017,28(4):414-426. |
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| 作者姓名： | 张志孝 郑栋 张义军 陆高鹏 |
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| 作者单位： | 1.中国气象科学研究院灾害天气国家重点实验室, 北京 100081 |
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| 基金项目： | 国家自然科学基金项目（41675005，91537209），中国气象科学研究院基本科研业务费重点项目（2016Z002） |
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| 摘 要： | 基于LMA三维闪电定位数据，对2004年10月5日发生于美国新墨西哥州的一次超级单体过程的闪电初始及其尺度特征进行研究，提出闪电初始阶段自动判别及其特征参量提取方法，并给出参量分布特征。结果显示:闪电初始阶段上行负先导（下行负先导）的持续时间中值为13.5 ms（7.5 ms），三维位移中值为1.4 km（1.0 km），三维平均位移速度中值为9.2×104 m·s-1（1.2×105 m·s-1），上行负先导速度随时间递减，下行反之，二者与垂直方向夹角的中值分别为40°和54°。表征闪电尺度的闪电凸壳面积和闪电总长度的概率密度呈负幂函数分布，在小值方向分布更为集中。闪电水平延展距离中值为6.1 km，垂直延展距离中值为4.3 km，约83%的闪电其水平延展距离大于垂直延展距离；闪电的持续时间中值为271.0 ms。分析发现，以水平延展为主的闪电起始高度分布峰值位于8.5 km，以垂直延展为主的闪电起始高度分布峰值位于11 km。闪电初始阶段位移方向越接近水平，对应闪电垂直延展越小，说明闪电初始段的传播方向对于闪电垂直延展具有重要影响。
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| 关 键 词： | 超级单体 闪电起始 闪电尺度 |
| 收稿时间： | 2017/2/13 0:00:00 |
| 修稿时间： | 2017/5/16 0:00:00 |
Identification Method and Analysis on Lightning Flash Initiation Phase and Size |
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| Zhang Zhixiao,Zheng Dong,Zhang Yijun and Lu Gaopeng.Identification Method and Analysis on Lightning Flash Initiation Phase and Size[J].Quarterly Journal of Applied Meteorology,2017,28(4):414-426. |
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| Authors: | Zhang Zhixiao Zheng Dong Zhang Yijun and Lu Gaopeng |
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| Affiliation: | State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081;Laboratory of Lightning Physics and Protection Engineering, Chinese Academy of Meteorological Sciences, Beijing 100081,State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081;Laboratory of Lightning Physics and Protection Engineering, Chinese Academy of Meteorological Sciences, Beijing 100081,State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081;Laboratory of Lightning Physics and Protection Engineering, Chinese Academy of Meteorological Sciences, Beijing 100081 and Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | Based on the observation of lightning mapping array, the statistical distribution of characteristic parameters describing the lightning flash initiation and size in a supercell storm occurring in New Mexico, United States on 5 October 2004 is studied. A method automatically identifying the start and end of the negative leaders in initial stage (IS) of lightning is developed. And the flash convex hull, total channel length, horizontal and vertical extent are used to represent the scale characteristics. Distributions and characteristics of flash initiation and size in this storm are shown as follows.Median values of the duration, three-dimensional displacement, vertical displacement and the average displacement velocity for the upward (downward) negative leaders during IS are 13.5 ms (7.5 ms), 1.4 km (1.0 km), 0.9 km (0.5 km), and 9.2×104 m·s-1 (1.2×105 m·s-1), respectively. In addition, the average flash initiation velocity decreases with height from 6 km to 11 km. With time going on, the speed of upward negative leader in initial stage decreases before 24 ms (to ensure the samples is larger than 100), while that of the downward negative leader increases before 12 ms (to ensure the samples is larger than 50). Moreover, negative leaders are dominantly tilted in initial stage, considering that the median angles between the 3-D displacement direction and the vertical direction are 40° for upward leader and 54° for downward leader, respectively.The probability density distribution of flash size described by flash convex hull and total channel length can be well fitted by negative power function, also showing that the distribution and evolution of flash convex hull is consist with that of total channel length. The median of flash duration is 271.0 ms, and the mean of that is 329.1 ms. The flash duration time and size are not significantly correlated. The flash with long duration time is not necessarily large. Moreover, the median of flash horizontal extent is 6.1 km while the vertical extent is 4.3 km, and there are 83% of flashes whose horizontal extent is greater than vertical extent. Flashes with horizontal extent greater than vertical extent are mainly initiated at 8.5 km high, and those with vertical extent greater than horizontal extent are mainly initiated at 11 km high. Greater horizontal displacement of the leader during initial stage accompanies less vertical extent, which indicates that the leader displacement direction at initial stage has an important influence on flash vertical scale. |
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| Keywords: | supercell flash initiation flash size |
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