## 1 Introduction  
With the increasing frequency of extreme global events and the continuous advancement of urbanization, lightning events have emerged as a major obstacle to the safe operation of cities and social-economic development. The advancement of lightning detection technology has facilitated in-depth analysis of the characteristics and causes of urban lightning activity, highlighting its significant scientific significance and practical application value [1, 2, 3]. During the process of urbanization, the population continues to gather in urban areas, leading to the expansion of the scale of the built-up areas. The urban underlying surface can alter the heat and momentum exchange in the boundary layer, and human activities emit air pollutants, ultimately shaping the local urban climate. The mechanisms by which urbanization impacts lightning activity primarily involve air pollutants, the urban thermal effect, the urban dynamic effect, and building morphology [4; 5; 6; 7; 8; 9; 10]. Some studies have found that air pollutants can enhance lightning activity by influencing the formation of ice particles and the development of convection [11; 12]. However, some scholars have concluded that there is no significant correlation between air pollutants and urban lightning activity [5; 13]. Research has even suggested that air pollutants can weaken lightning activity through radiation effects [14]. Further exploration may be necessary to establish whether aerosols play a role in either promoting or mitigating lightning activity. With regard to the urban thermal effect, numerous scholars have made valuable discoveries [15; 16]. [PERSON] et al. [17] were the first to note that the UHI effect can modulate lightning activity. Simulation results from a mesoscale model (MM5) in the Atlanta area showed that the urban heat island (UHI) can trigger and enhance thunderstorms, with thunderstorms primarily concentrated in the urban center [18]. [PERSON] et al. [19] conducted sensitivity tests on urban surface parameters and found that as the UHI intensity weakens, there are significant changes in the center of thunderstorm activity. Under the influence of weak synoptic backgrounds, the UHI effect causes disturbance in the city, which plays a dominant role in triggering local convection [20]. Scholars have concluded that the urban thermal effect can promote the development of a mixed boundary layer and assist in triggering thunderstorms [12]. However, some scholars have acknowledged that the contribution of the UHI effect to thunderstorm development is not evident [21; 22]. The urban underlying surface, with its roughness, can alter the structure and motion of the near-surface atmospheric layer in cities through dynamic interactions [23; 24], which then has a significant impact on weather processes within the urban area and the surrounding regions [25; 26]. A limited number of scholars have emphasized that the barrier effect can facilitate the bifurcation and detouring of thunderstorms [27], leading to the concentration of lightning activity at the periphery of built-up areas [28]. Preliminary investigations into the causes of the urban barrier effect have been conducted from a climatological perspective [17; 29]. During periods when the urban heat island (UHI) is weak, summer thunderstorms are observed to bifurcate and bypass the city [30]. Moreover, when ground wind speeds are high, the urban barrier effect on thunderstorms becomes particularly pronounced [29]. The development of thunderstorm systems is also closely linked to larger-scale synoptic conditions [31]. When thunderstorms with strong frontal synoptic backgrounds pass through the city, the central city density of cloud-to-ground (CG) lightning flashes tends to be lower [28]. However, some studies have observed the opposite, finding that even under weak synoptic conditions, thunderstorms passing through urban areas can bifurcate [26].