High‐speed video observation of stepwise propagation of a natural upward positive leader

Journal of Geophysical Research D: Atmospheres - Tập 121 Số 24 - 2016
Zhichao Wang1,2, Xiushu Qie3,1, Rubin Jiang3,1, Caixia Wang4, Gaopeng Lu3,1, Zhuling Sun1, Mingyuan Liu1, Yunjiao Pu5,1
1Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2Meteorological Observation Centre, China Meteorological Administration, Beijing, China
3Collaborative Innovation Centre on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing, China
4Beijing Information Science and Technology University, Beijing, China
5College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, China

Tóm tắt

AbstractUsing a high‐speed video camera operated at 150,000 frames per second, we have documented the upward propagation of an initial positive leader from a 325 m meteorological tower in Beijing. The stepwise development of the upward positive leader was clearly revealed during its self‐sustained propagation toward the cloud base, providing the first optical evidence for the stepping processes of a positive leader. The leader developed with definitive intermittent pauses and re‐establishment with abrupt jump of the leader top. Obvious brush‐like corona zone emitting outward from the leader top was identified in the frame of stepping, and the luminosity waves propagated downward along the already formed channel from the leader top immediately following the stepping, indicating that a current wave was generated at the leader top and subsequently traveled down the channel. The channel luminosity decreased during the leader pause stage, with the corona zone dimmed correspondingly. The positive leader experienced an average interstep interval of 61.7 µs (ranging between 30 µs and 120 µs) and an average 2‐D speed of 8.1 × 104 m/s. The transient speed of the step jump was estimated to be larger than 7.3 × 105 m/s with an average step length of 4.9 m. The need of sufficient positive charge accumulation at the leader top could be the main cause for the stepping characteristics.

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Journal of Geophysical Research D: Atmospheres

Tập 121 Số 24

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