Quantitative Analysis of Relative Humidity Effects on Atmospheric Visibility in Chengdu Megacity, Sichuan

Although air quality in Chengdu, a mega city in the Sichuan Basin, has improved due to reductions in PM2.5, haze events continue to occur frequently. This study quantifies aerosol dry mass extinction efficiency and the RH-induced extinction to visibility degradation in the city. A Monte Carlo simulation framework constrained by observational data is developed to estimate PM2.5 thresholds for haze-free conditions (visibility ≥ 10 km) under high RH scenarios, which can offer a basis for developing adaptive air quality and visibility management strategies in Chengdu and other high-RH urban regions.