Assessment of aerosol direct effects on PM2.5 and O3 air quality in Continental Southeast Asia

Abstract

An online coupled modeling system composed of Weather Research and Forecasting (WRF) model and Community Multiscale Air Quality (CMAQ) model was applied to assess aerosol direct effects on air quality with the focus on fine particulate matter (PM2.5) and ozone (O3) in Continental Southeast Asia where has suffered significant air pollution recently due to rapid development. The results showed that, in four focused countries including Cambodia, Laos, Thailand, and Vietnam, the direct effects moderately decreased shortwave radiation, temperature, planetary boundary layer (PBL) height, and wind speed by -9.08%, -0.44°C, -10.27%, and -2.21% in dry season, and -2.37%, -0.04°C, -2.05%, and -0.57% in wet season, respectively. Consequently, PM2.5 concentration was found to increase by +10.51% in dry season and +1.44% in wet season. O3 concentration was decreased by -2.76% in dry season while slightly increased by +0.56% in wet season. The increasing effect of aerosols on PM2.5 concentration was caused by the more stable atmospheric condition. The increase or decrease in O3 concentration depended on the responses of atmospheric dynamics as well as photolysis rates of photochemical reactions to direct effects.