Classification and investigation of Asian aerosol properties
1Department of Atmospheric Science, University of North Dakota, Grand Forks, ND, USA
2GCESS, Beijing Normal University, Beijing, China
3Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA
Abstract. Ongoing urbanization and industrialization in East Asia have generated a wide variety of aerosols in the atmosphere and have consequently added more uncertainty when evaluating global climate change. To classify different types of aerosols and investigate their physical and chemical properties, four AErosol RObotic NETwork (AERONET) sites have been selected to represent aerosol properties dominated by mixed complex particle types (Xianghe and Taihu), desert-urban (SACOL), and biomass (Mukdahan) over East Asia during the 2001–2010 period. The volume size distribution, aerosol optical depth [τ (λ) and τabs(λ)], Ångström exponent (α and αabs), and the single scattering co-albedo [ωoabs(λ)] and α(ωoabs) parameters over the four selected sites have been analyzed. These parameters are used to (a) investigate the aerosol properties and their seasonal variations over the four selected sites, (b) discern the different absorptive characteristics of BC, OC, and mineral dust particles using αabs440-870 and α (ωoabs440-870), and (c) develop an aerosol clustering method involving α440-870 and ωoabs440. A strong mineral dust influence is seen at the Xianghe, Taihu, and SACOL sites during the spring months (MAM) as given by coarse mode size distribution dominance, declining α440-870, and elevated αabs440-870 and α (ωoabs440-870) values. A weakly absorbing pollution (OC and biomass) aerosol dominance is seen in the summer (JJA) and autumn (SON) months as given by a strong fine mode influence, increasing α440-870, and declining αabs440-870 and α (ωoabs440-870) values. A winter season (DJF) shift toward strongly absorbing BC particles is observed at Xianghe and Taihu (elevated α440-870, increase in αabs440-870 and α(ωoabs440-870)). At Mukdahan, a fine mode biomass particle influence is observed year round as given by the volume size distribution, elevated α440-870 (higher than the other sites), low αabs440-870 and negative α (ωoabs440-870) values indicating weakly absorbing OC particles. The α(ωoabs) parameter is also shown to have less overlap in values than αabs in discerning influences from OC, BC, biomass and mineral dust particles. The clustering method using α440-870 and ωoabs440 illustrates four groups of aerosols: Cluster I – fine mode, weakly absorbing pollution particles, Cluster II – fine mode, strongly absorbing pollution particles, Cluster III – coarse mode, strongly absorbing mineral dust particles, and Cluster IV – biomass particles with similar characteristics as Cluster II but less absorbing. This method has shown that aerosol mixtures are both seasonal and regional combinations of particles that were either locally generated or transported from other source regions and should be implemented over other AERONET sites in the future.