Articles | Volume 17, issue 8
Research article
24 Apr 2017
Research article |  | 24 Apr 2017

Ground-based characterization of aerosol spectral optical properties of haze and Asian dust episodes under Asian continental outflow during winter 2014

Jinsang Jung, JeongAh Yu, Youngsook Lyu, Minhee Lee, Taekyung Hwang, and Sangil Lee

Abstract. Long-range transported (LRT) haze can affect the regional radiation budget and the air quality in areas downwind of the Asian continental outflow. Because in situ observations of spectral aerosol optical properties of the LRT haze are rare, an intensive characterization of aerosol optical properties is needed. This study characterized the spectral optical properties of the LRT haze and Asian dust originating from the Asian continent. Integrated chemical and optical measurements of aerosol particles were carried out in a downwind area of the Asian continental outflow (Daejeon, South Korea) during winter 2014. High concentrations of PM10 (particulate matter with a diameter  ≤  10 µm) and light scattering coefficients at 550 nm, σs, 550, were observed during a long-range transport (LRT) haze episode (PM10 =  163.9 ± 25.0 µg m−3; σs, 550 =  503.4 ± 60.5 Mm−1) and Asian dust episode (PM10 =  211.3 ± 57.5 µg m−3; σs, 550 =  560.9 ± 151 Mm−1). During the LRT haze episode, no significant change in the relative contribution of PM2. 5 (particulate matter with a diameter  ≤  2.5 µm) chemical components was observed as particles accumulated under stagnant atmospheric conditions (13–17 January 2014), suggesting that the increase in PM2. 5 mass concentration was caused mainly by the accumulation of LRT pollutants. On the other hand, a gradual decrease in Ångström exponent (Å) and a gradual increase in single scattering albedo (ω) and mass scattering efficiency (MSE) were observed during the stagnant period, possibly due to an increase in particle size. These results imply that a change in particle size rather than chemical composition during the stagnant period is the dominant factor affecting the aerosol optical properties. During the Asian dust episode, a low PM2. 5 ∕ PM10 ratio and Å(450∕700) were observed with average values of 0.59 ± 0.06 and 1.08 ± 0.14, respectively, which were higher than those during the LRT haze episode (0.75 ± 0.06 and 1.39 ± 0.05, respectively), indicating that PM2. 5 ∕ PM10 mass ratios and Å(450∕700) can be used as tracers to distinguish aged LRT haze and Asian dust under the Asian continental outflow.

Short summary
No significant change in PM2.5 chemical components was observed during the accumulation. The increase in single scattering albedo is mainly due to an increase in particle size. Å of scattering can be used as a tracer to distinguish transported haze and Asian dust.
Final-revised paper