Characteristics of Lightning Activity in Southeast China and its Relation to the Atmospheric Background

Based on the lightning observation data from the Fengyun-4A (FY-4A) Lightning Mapping Imager (FY-4A/LMI) and the Lightning Imaging Sensor (LIS) on the International Space Station (ISS), we extract the "event" type data as the lightning detection results. These observations are then compared with the cloud-to-ground (CG) lightning observation data from the China Meteorological Administration. This study focuses on the characteristics of lightning activity in Southeast China, primarily in Jiangxi Province and its adjacent areas, from April to September, 2017–2022. In addition, with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis data, we further delved into the potential factors influencing the distribution and variations in lightning activity and their primary related factors. Our findings indicate that the lightning frequency and density of the FY-4A/LMI, ISS-LIS and CG data are higher in southern and central Jiangxi, central Fujian Province, and western and central Guangdong Province, while they tend to be lower in eastern Hunan Province. In general, the high-value areas of lightning density for the FY-4A/LMI are located in inland mountainous areas. The lower the latitude is, the higher the CG lightning density is. High-value areas of the CG lightning density are more likely to be located in eastern Fujian and southeastern Zhejiang Province. However, the high-value areas of lightning density for the ISS-LIS are more dispersed, with a scattered distribution in inland mountainous areas and along the coast of eastern Fujian. Thus, the mountainous terrain is closely related to the high-value areas of the lightning density. The locations of the high-value areas of the lightning density for the FY-4A/LMI correspond well with those for the CG observations, and the seasonal variations are also consistent. In contrast, the distribution of the high-value areas of the lightning density for the ISS-LIS is more dispersed. The positions of the peak frequency of the FY-4A/LMI lightning and CG lightning contrast with local altitudes, primarily located at lower altitudes or near mountainsides. K-index and convective available potential energy (CAPE) can better reflect the local boundary layer conditions, where the lightning density is higher and lightning seasonal variations are apparent. There are strong correlations in the annual variations between the dew-point temperature (T_d) and CG lightning frequency, and the monthly variations of the dew-point temperature and CAPE are also strongly correlated with monthly variations of CG lightning, while they are weakly correlated with the lightning frequency for the FY-4A/LMI and ISS-LIS. This result reflects that the CAPE shows a remarkable effect on the CG lightning frequency during seasonal transitions.