Optical properties of tropospheric aerosols based on measurements of lidar, sun-photometer, and visibility at Chung-Li (25°N, 121°E)

We have used lidar, sun-photometer, and the visibility measurements to investigate the optical properties of aerosols in the lower air. The observations were performed at Chung-Li (25°N, 121°E) during the period of February 2002–May 2004. Combined data indicate that 40–50% of total extinction in the column air contributed by aerosols in 1–5 km. Seasonally, spring time extinction is higher than other seasons. However, the summer extinction is the highest below about 2 km. Sources for aerosols are determined by using satellite imageries and back trajectories. Aerosols backscattering ratio and depolarization ratio are then categorized based on their sources. We found that the largest optical thickness is biomass burning aerosols originated in Southeast Asia. The aerosols generated from Northern China transported by the high-pressure system in spring are usually dust with depolarization ratios in the range of 0.1–0.3, but varying backscattering coefficients. The aerosols optical characteristics will be useful for future understanding about their environmental and climate effects.