Impact of Air Pollutants on Lightning Activities in Kathmandu, Nepal

An electric field mill (EFM-100) short-range sensor has been installed on the rooftop of the six story building of Kathmandu BernHardt College, Tribhuvan University (TU), Bafal, Kathmandu for continuous monitoring of lightning events within a 38 km in aerial distance. It constantly monitors lightning activities and activates graphical display alerts on a connected computer. The EFM-100 monitor software displays a real time graph of the atmospheric electrical field, as well as the distance of lightning strikes within the specified range. Lightning strikes were recorded over a 3-month period, spanning 57 days, primarily during the both premonsoon and monsoon seasons, from May 19 to August 18, 2024. In addition, the effect of lightning events on atmospheric pollutants such as PM₁, PM_2.5, PM₁₀, relative humidity, temperature, and particle density of ozone per cubic centimeter were analyzed. These atmospheric parameters were obtained from the Central Department of Environment Science, TU, Nepal. The results clearly show that the atmospheric pollutants PM₁, PM_2.5, and PM₁₀, found to be higher during the lightning events. PM_2.5 concentrations increased by an average of approximately 18%, PM₁₀ by about 12%, and ozone by about 22% compared with prelightning background levels. Similarly, the atmospheric temperature increased by 1.5°C-2.0°C during the strong lightning events followed by a gradual decrease thereafter. These findings provide clear evidence of the magnitude of pollutants and thermal changes associated with lightning. It was also observed that relative humidity is inversely proportional to temperature, as it rises due to lightning phenomena. Furthermore, lightning activity was found to significantly increase with rising concentrations of ozone particles in the atmosphere.