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

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.