Comparison of key absorption and optical properties between pure and transported anthropogenic dust over East and Central Asia
Abstract. Asian dust particulate is one of the primary aerosol constituents in the Earth–atmosphere system that exerts profound influences on environmental quality, human health, the marine biogeochemical cycle, and Earth's climate. To date, the absorptive capacity of dust aerosol generated from the Asian desert region is still an open question. In this article, we compile columnar key absorption and optical properties of mineral dust over East and Central Asian areas by utilizing the multiyear quality-assured datasets observed at 13 sites of the Aerosol Robotic Network (AERONET). We identify two types of Asian dust according to threshold criteria from previously published literature. (1) The particles with high aerosol optical depth at 440 nm (AOD440 ≥ 0.4) and a low Ångström wavelength exponent at 440–870 nm (α < 0.2) are defined as Pure Dust (PDU), which decreases disturbance of other non-dust aerosols and keeps high accuracy of pure Asian dust. (2) The particles with AOD440 ≥ 0.4 and 0.2 < α < 0.6 are designated as Transported Anthropogenic Dust (TDU), which is mainly dominated by dust aerosol and might mix with other anthropogenic aerosol types. Our results reveal that the primary components of high AOD days are predominantly dust over East and Central Asian regions, even if their variations rely on different sources, distance from the source, emission mechanisms, and meteorological characteristics. The overall mean and standard deviation of single-scattering albedo, asymmetry factor, real part and imaginary part of complex refractive index at 550 nm for Asian PDU are 0.935 ± 0.014, 0.742 ± 0.008, 1.526 ± 0.029, and 0.00226 ± 0.00056, respectively, while corresponding values are 0.921 ± 0.021, 0.723 ± 0.009, 1.521 ± 0.025, and 0.00364 ± 0.0014 for Asian TDU. Aerosol shortwave direct radiative effects at the top of the atmosphere (TOA), at the surface (SFC), and in the atmospheric layer (ATM) for Asian PDU (α < 0.2) and TDU (0.2 < α < 0.6) computed in this study, are a factor of 2 smaller than the results of Optical Properties of Aerosols and Clouds (OPAC) mineral-accumulated (mineral-acc.) and mineral-transported (mineral-tran.) modes. Therefore, we are convinced that our results hold promise for updating and improving accuracies of Asian dust characteristics in present-day remote sensing applications and regional or global climate models.
