Classification and investigation of Asian aerosol absorptive properties

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 τ<sub>abs</sub>), Ångström exponent (α and α<sub>abs</sub>), and the single scattering co-albedo (ω<sub>oabs</sub>) 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 α<sub>440–870</sub> < 1, and mean α<sub>abs440–870</sub> > 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, α<sub>440–870</sub> > 1, and α<sub>abs440–870</sub> < 1.5. A winter season (DJF) shift toward strongly fine mode, absorbing particles (BC and OC) is observed at Xianghe and Taihu (α<sub>abs440–870</sub> > 1 and α<sub>abs440–870</sub> > 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 α<sub>440–870</sub> and ω<sub>oabs440</sub> 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

Comparing multiple model-derived aerosol optical properties to spatially collocated ground-based and satellite measurements

“…Concurrently, the AERONET data show a drop in SSA and a peak in α that is extremely consistent with the models and suggestive of carbonaceous particles from burning. Because of the lack of moisture during the winter dry season, the peak in α may also be attributed to the lack of hygroscopic growth (Logan et al, 2013). The models also show a slight increase in dust AOD during summer in Mukdahan (not shown), which matches up well with a sharp dip in AERONET α.…”

Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season

“…This result indicates that aerosols mostly consist of dust, smoke, and polluted dust during the monsoon season in South Asia, hence attaining consistency with previous work [44]. These aerosols present distinct absorbing effects on solar radiation, thereby attenuating the incoming solar radiation more intensively than other types of aerosols [45]. The incident SW radiation at the surface is highly negatively correlated with aerosol loading [15,46].…”

Similarities and differences of aerosol optical properties between southern and northern sides of the Himalayas

“…Some studies have successfully combined SSA with other parameters to determine the aerosol type over different regions (Lee et al, 2010;He et al, 2012b;Logan et al, 2013). However, over regions with low aerosol load (AOD 440 nm < 0.40) it is difficult to obtain aerosol type by SSA due to inadequate accuracy (Dubovik and King, 2000).…”