FY-4A和地基闪电数据在京津冀地区的对比

Comparison of FY-4A Satellite LMI Data and Ground-based Lightning Detection Data in Beijing-Tianjin-Hebei Region

  • 摘要: 基于2021—2023年4—8月FY-4A气象卫星LMI闪电组(简称LMI闪电)和国家雷电探测系统DDW1闪电电磁脉冲(简称DDW1闪电)数据,通过数据一致率敏感性试验确定时空匹配窗口,分析二者在京津冀地区的时空分布和匹配特征。结果表明:DDW1闪电样本量较LMI闪电偏大1个量级。DDW1闪电密度空间分布相对集中,存在明显海陆差异;LMI闪电密度分布相对分散,在海洋和陆地上较均匀。DDW1闪电样本量日变化峰值出现在16:00—17:00(北京时,下同),谷值出现在09:00—10:00,LMI闪电在19:00—20:00最多,在13:00—14:00最少。时空匹配阈值取为2 s和50 km时,与DDW1闪电相匹配的LMI闪电占比为48.6%,其辐射亮度约为不匹配的LMI闪电的2倍,并与DDW1负地闪雷电流幅值呈负相关。与DDW1闪电相匹配的LMI闪电多集中在京津冀东部,不匹配的LMI闪电多位于太行山及燕山山脉、山东中部山地和渤海中部。白天LMI探测到的闪电数量虽少但辐射亮度大,伴随较强雷电流,可匹配LMI闪电的占比较高;夜间有超过一半的LMI闪电未被DDW1探测系统捕捉到。

     

    Abstract: Based on lightning groups detected by lightning mapping imager (LMI) of FY-4A meteorological satellite and lightning electromagnetic pulse (LEMP) detected by DDW1 sensors of national lightning detection system from April to August during 2021-2023, spatial and temporal distributions and matching characteristics of these two datasets are analyzed for Beijing-Tianjin-Hebei Region. Results indicate that the frequency of DDW1-detected LEMP is roughly one order of magnitude higher than that of LMI-detected lightning groups, suggesting a generally higher detection efficiency of DDW1 in the target area. The spatial distribution of DDW1-detected LEMP is relatively concentrated with significant land-sea differences, while LMI-detected lightning groups are more dispersed and evenly distributed across the Bohai Sea and land areas. Monthly variations of lightning frequency detected by DDW1 and LMI are generally consistent, The diurnal variation of DDW1-detected LEMP peaks at 1600-1700 BT and reaches its minimum at 0900-1000 BT, while LMI-detected lightning groups are most frequent at 1900-2000 BT and least frequent at 1300-1400 BT. LMI exhibits significantly weaker efficiency during daytime compared to nighttime. Using spatiotemporal matching thresholds of 2 s and 50 km, 48.6% of LMI lightning groups match with DDW1 LEMP signals. The matched LMI-detected lightning groups exhibit higher average radiance (approximately twice that of unmatched groups) and larger current amplitudes in DDW1-detected cloud-to-ground lightning (CG). A significant negative correlation is observed between the radiance of matched LMI-detected lightning groups and the current intensity of matched DDW1-detected negative CG, indicating that higher radiance is associated with stronger negative current intensity. The matched LMI-detected lightning groups are predominantly concentrated in the eastern part of Beijing-Tianjin-Hebei Region, while unmatched lightning groups are frequently observed near the Taihang and Yanshan mountainous ranges, the central Bohai Sea and mountainous areas of central Shandong Province. The proportion of LMI-detected lightning groups that match with DDW1-detected LEMP is higher during daytime and lower at night. Although fewer lightnings are detected by LMI during daytime, they exhibit higher radiance and are often accompanied by strong lightning currents, making them more readily detectable by DDW1. Associated with weaker lightning currents, LMI-detected lightning groups have lower radiance at night, resulting in approximately half of them remaining undetected by DDW1.

     

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