Effect of Large-scale Biomass Burning on Aerosol Optical Properties at the GAW Regional Station of Pha Din, Vietnam

Nicolas Bukowiecki ； Martin Steinbacher ； Stephan Henne ； Nguyen Nhat Anh ； Xuan Anh Nguyen ； Anh Le Hoang ； Dac Loc Nguyen ； Duong Hoang Long ； Guenter Engling ； Günther Wehrle ； Martin Gysel ； Urs Baltensperger

《Aerosol and Air Quality Research》 19卷5期 (2019/05) Pp. 1172-1187

https://doi.org/10.4209/aaqr.2018.11.0406

摘要

In 2014, Pha Din (1466 m a.s.l.) was established as a Global Atmosphere Watch (GAW) regional station for aerosol and trace gas measurements in northwestern Vietnam. This study presents a five-year climatology of aerosol optical properties derived from nephelometer and aethalometer measurements and a comparison with ground-based remote sensing measurements at the nearby AERONET station of Son La. The annual variations of the aerosol measurements at Pha Din are clearly dominated by annually recurring periods with high biomass burning activity in northern Southeast Asia (February-May). During these periods, a large majority of air masses arriving at Pha Din originate to the southwest (northern Thailand, Laos and Myanmar). Both the meteorological conditions and the aerosol optical properties are very similar between individual periods (increased temperature: ＞ 20°C; moderate ambient relative humidity: 60-70%; decreased single scattering albedo: 0.8-0.9; increased absorption Ångström exponent: 1.6-2.0; and scattering Ångström exponent: ＞＞ 1). Prior to the biomass burning season (October-January), the meteorological conditions at Pha Din are influenced by the SE Asian monsoon, leading to the frequent transport of air masses from SW China with moderate aerosol loadings. The lowest pollution levels are observed from June to September, which represents the wet season.

關鍵字

Aerosol optical properties ； Biomass burning ； Black carbon ； Long-term measurements ； Global Atmosphere Watch