A comparison of dust properties between China continent and Korea, Japan in East Asia

摘要

The optical properties of Asian dust were examined from the Aerosol Robotic Network (AERONET) measurements at 10 sites during 2001-2005. A comparison of dust properties was performed between China continent as source regions and Korea, Japan as downwind regions where the dust properties were influenced by long-range transport. Higher aerosol optical thicknesses (AOT) appeared at Chinese sites than Korean and Japanese sites associated with lower Angstroem exponents (α). The value of α decreased with increasing AOTs, and decreased to zero or negative when the heavy dust events occurred especially in source regions. The aerosol volume size distributions showed a tri-modal structure, one accumulation mode with radius 0.07 μm and two coarse modes with radii 1.3 and 2.9-3.8 μm in source regions, one accumulation mode with radius 0.09 μm and two coarse modes with radii 1.3-2.2 and 2.9-3.8 μm in downwind regions. In view of climate, the single scattering albedo (SSA) at 440, 670, 870 and 1020 nm was used as 0.95 in source regions of China, and in downwind regions such as 0.92 of Korea and 0.95 of Japan. The real parts of refractive index showed a behavior of low sensitivity to wavelengths, 1.51 in source regions of China, and in downwind regions 1.45 of Korea and 1.39 of Japan at the same four wavelengths. The imaginary parts also showed a low sensitivity to wavelengths, with values of 0.0015-0.0044 in source regions and 0.0018-0.0052 in downwind regions at the four wavelengths. The asymmetry factors at the four wavelengths were used as 0.67 over source and downwind regions in climate and radiation models. This difference in dust properties between source regions and downwind regions was mainly attributed to the impacts of dry depositing and wet scavenging during the long-range transport of dust plume.