Studying the optical and physical properties of aerosolin an urban area of Hanoi city

Abstract

The purpose of this study is to analyse and evaluate the optical and physical properties of aerosol in an urban area of Hanoi city based on the data products for aerosol characteristics measured by the sunphotometer situated at the ground station (Nghia Do AERONET station, Hanoi) and by the MODIS satellite remote sensing for 3 seasons (dry, rainy, and transitional seasons) during the period of 2010-2018. The findings showed that the aerosol optical depth (AOD) has the highest value in the transitional season (1.24), followed by those in the dry (0.94) and rainy (0.57) seasons. The high value of Angstrom Exponent (1.34) measured at the wavelengths of 870 and 440 nm (AE440-870) indicated the major contribution of fine particles, compared to that by the coarse particles, in the aerosol loading in the study area. The high values of both Extinction Angstrom Exponent (EAE440-480) and Absorbed Angstrom Exponent (AAE440-480) during 3 seasons suggested that aerosol originated from both biomass burning and urban/industrial sources co-existed in the atmosphere in the study area. The analysis results for active fires in the Southeast Asia measured by MODIS satellite and air mass backward trajectories arrived at the study site in Hanoi in the periods of 2016 showed that the regional biomass burning activities (the central region of Vietnam and neighboring countries including Thailand, Laos, and Cambodia) could be the important source influencing the variation of optical and physical properties of aerosol during the end of the dry season and transitional season in the urban area of Hanoi city.