Abstract
We use five years (2009 – 2013) of multiwavelength Raman lidar measurements at Gwangju, Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust in dependence of its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Angstrom exponents (wavelength pair 355/532nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modelling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground in which these plumes were transported: (I) the dust layers passed over China at high altitude levels until arrival over Gwangju, and (II) the Asian dust layers were transported near the surface and the lower troposphere over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ in dependence of their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21±0.06 (at 532 nm), the mean lidar ratios were 52±7 sr at 355 nm and 53±8 sr at 532 nm, and the mean Angstrom exponent was 0.74±0.31 in case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios, and higher lidar ratio and Angstrom exponents. The mean linear particle depolarization ratio was 0.13 ± 0.04, the mean lidar ratios were 63±9 sr at 355 nm and 62±8 sr at 532 nm, respectively, and the mean Angstrom exponent was 0.98±0.51. These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution.
Highlights
The main objective of this study is to investigate the variation of optical properties of mixtures of Asian dust with anthropogenic pollution in dependence of the pathways and vertical distributions of these mixed dust layers during long-range transport
East Asian dust is complicated as it usually travels over densely populated and highly industrialized areas of China before it moves out over Pacific Ocean
There still is a lack of understanding of how much of the mixing of dust with pollutants depends on the vertical distribution over East Asia when dust passes over source regions of anthropogenic pollution
Summary
The main objective of this study is to investigate the variation of optical properties of mixtures of Asian dust with anthropogenic pollution in dependence of the pathways and vertical distributions of these mixed dust layers during long-range transport. Case I includes those Asian dust plumes that passed over industrialized areas in China at high altitude level (bottom panel) Scatter diagram of the linear particle depolarization at 532 nm versus (c) the backscatterrelated Ångström exponent (355/532 nm wavelength pair), and the (d), (e) lidar ratio (at 355 nm and at 532 nm) with respect to the Case I and Case II.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
