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Abstract Bangkok, Thailand is a tropical Asian megacity with high aerosol concentrations and frequent thunderstorm activity. This investigation examines the covariation between thermodynamics, aerosols, and thunderstorms, using lightning stroke counts as a measure of intensity, for a five-year period (2016–2020). The investigation incorporates data from the aerosol robotic network (AERONET), ERA-5 reanalysis, ground-based air quality stations, and total lighting data from Vaisala Inc.’s GLD360 network to examine the aerosol-thermodynamic interrelationships within thunderstorm initiation environments. Results indicate that aerosol impacts on thunderstorms are robust and, when examined in concert with instability, can augment lightning. Thermodynamic instability is also positively correlated with stroke counts in thunderstorms. Particulate matter greater than 10 µg m^-3(PM10) concentration is significantly higher in thunderstorms containing more than 100 strokes, supporting the potential role of aerosols in promoting the non-inductive charge process. The emergence of a “boomerang” or threshold effect is also evident as aerosol optical depth (AOD) increases. Evidence suggests increasing AOD initially promotes, then limits, instability and thunderstorm intensity. Finally, there exists a positive relationship between aerosol concentration and particle size in thunderstorm initiation environments. 

A multi-variable investigation of thunderstorm environments in two distinct geographic regions is conducted to assess the aerosol and thermodynamic environments surrounding thunderstorm initiation. 12-years of cloud-to-ground (CG) lightning flash data are used to reconstruct thunderstorms occurring in a 225 km radius centered on the Washington, DC. and Kansas City Metropolitan Regions. A total of 196,836 and 310,209 thunderstorms were identified for Washington, D.C. and Kansas City, MO, respectively. Hourly meteorological and aerosol data were then merged with the thunderstorm event database. Evidence suggests, warm season thunderstorm environments in benign synoptic conditions are considerably different in thermodynamics, aerosol properties, and aerosol concentrations within the Washington, D.C. and Kansas City regions. However, thunderstorm intensity, as measured by flash counts, appears regulated by similar thermodynamic-aerosol relationships despite the differences in their ambient environments. When examining thunderstorm initiation environments, there exists statistically significant, positive relationships between convective available potential energy (CAPE) and flash counts. Aerosol concentration also appears to be a more important quantity than particle size for lightning augmentation. 

This investigation builds upon and extends prior lightning research in the Bangkok Metropolitan Region (BMR) through the reconstruction of thunderstorm distribution, utilizing a novel lightning tracking algorithm. Five years (2016–2020) of lightning stroke data from the Global Lightning Dataset (GLD360) were used to identify 52 608 thunderstorms. Optimized hotspot analyses, track densities, and analyses of thunderstorms with respect to winds, landcover, and seasons were performed. Our findings suggest that significant modification of thunderstorm distribution within the region was due to urban landcover impacts on the local environment. Thunderstorm intensity, as measured by stroke counts and track length, also appeared to be sensitive to the urban environment. The thunderstorm distribution also highlighted areas prone to hazards such as flash flooding. By visualizing thunderstorms grouped by winds, thunderstorm initiation hotspots and track density corridors were identified. These corridors of augmented thunderstorm production tended to occur during specific months given the seasonal monsoon wind regime occurring across the BMR. As urbanization within the BMR continues, geospatial assessment of thunderstorms is important to inform forecast meteorologists, urban planners, government officials, and others who play a critical role in developing strategies, policies and insfrastructure that could mitigate thunderstorm impacts.