Abstract
Abstract. Asian aerosols are among the most complex yet widely studied components of the atmosphere not only due to their seasonal variability but also their effects on climate change. Four Aerosol Robotic Network (AERONET) sites have been selected to represent aerosol properties dominated by pollution (Taihu), mixed complex particle types (Xianghe), desert-urban (SACOL), and biomass (Mukdahan) in East Asia during the 2001–2010 period. The volume size distribution, aerosol optical depth (τ and τabs), Ångström exponent (α and αabs), and the single scattering co-albedo (ωoabs) parameters over the four selected sites have been used to (a) illustrate seasonal changes in aerosol size and composition and (b) discern the absorptive characteristics of black carbon (BC), organic carbon (OC), mineral dust particles, and mixtures. A strongly absorbing mineral dust influence is seen at the Xianghe, Taihu, and SACOL sites during the spring months (MAM), as given by coarse mode dominance, mean α440–870 < 1, and mean αabs440–870 > 1.5. There is a shift towards weakly absorbing pollution (sulfate) and biomass (OC) aerosol dominance in the summer (JJA) and autumn (SON) months, as given by a strong fine mode influence, α440–870 > 1, and αabs440–870 < 1.5. A winter season (DJF) shift toward strongly fine mode, absorbing particles (BC and OC) is observed at Xianghe and Taihu (αabs440–870 > 1 and αabs440–870 > 1.5). At Mukdahan, a strong fine mode influence is evident year round, with weakly and strongly absorbing biomass particles dominant in the autumn and winter months, respectively, while particles exhibit variable absorption during the spring season. A classification method using α440–870 and ωoabs440 is developed in order to infer the seasonal physico-chemical properties of the aerosol types, such as fine and coarse mode, weak and strong absorption, at the four selected Asian sites.
Highlights
Geoscientific Instrumentation anghe), desert-urban (SACOL), and biomass (Mukdahan) inEast Asia during the 2001–2010 period
Mineral dust influences are clearly seen at Xianghe, Taihu, and SACOL, primarily during the spring months (MAM) as illustrated by the large coarse mode particle volume distribution, low α440−870, and elevated αabs440−870
During the summer months (JJA), there is a shift towards fine mode, weakly absorbing aerosols derived primarily from anthropogenic sources as given by an increase in the fine mode particle volume distribution, high α440−870, and low αabs440−870 values at Xianghe, Taihu, and SACOL
Summary
Geoscientific Instrumentation anghe), desert-urban (SACOL), and biomass (Mukdahan) in. Previous studies have suggested that it is possible to reduce the ambiguities in identifying aerosol composition by using the parameters aerosol optical depth [τ (λ)], aerosol absorption optical depth [τabs(λ)], Angstrom exponent (α), and the single scattering albedo [ωo(λ)] (Russell et al, 2010; Lewis et al, 2008; Bergstrom et al, 2007; Jeong and Li, 2005; Higurashi and Nakajima, 2002) These methods, are dependent upon the total volume extinction and absorption (βext and βabs) of all particles present in an aerosol mixture. The current study will use particle volume size distribution, the τ440, τabs440, α, αabs, ωo, and the single scattering co-albedo (1-ωo or known as ωoabs) parameters to (1) report the relative influence and seasonal variation of aerosols at the four Asian AERONET sites, and (2) infer how their composition is a likely combination of multiple constituents (e.g., BC, OC, sulfate, and mineral dust particles).
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