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Measurements of the Lidar Ratio for Asian Dust and Pollution Aerosols with a Combined Raman and Back-scatter Lidar  

Yoon, S.C. (School of Earth and Environmental Sciences, Seoul National University)
Lee, Y.J. (School of Earth and Environmental Sciences, Seoul National University)
Kim, S.W. (School of Earth and Environmental Sciences, Seoul National University)
Kim, M.H. (School of Earth and Environmental Sciences, Seoul National University)
Sugimoto, N. (Atmospheric Environment Division, National Institute for Environmental Studies)
Publication Information
Atmosphere / v.20, no.4, 2010 , pp. 483-494 More about this Journal
Abstract
The vertical profiles of the extinction coefficient, the backscatter coefficient, and the lidar ratio (i.e., extinction-to-backscattering ratio) for Asian dust and pollution aerosols are determined from Raman (inelastic) and elastic backscatter signals. The values of lidar ratios during two polluted days is found between 52 and 82 sr (July 22, 2009) and 40~60 sr (July 31, 2009) at 52 nm, with relatively low value of particle depolarization ratio (<5%) and high value of sun photometer-derived Angstrom exponent (> 1.2). However, lidar ratios between 25 and 40 sr are found during two Asian dust periods (October 20, 2009 and March 15, 2010), with 10~20% of particle depolarization ratio and the relatively low value of sun photometer-derived Angstrom exponent (< 0.39). The lidar ratio, particle depolarization ratio and color ratio are useful optical parameter to distinguish non-spherical coarse dust and spherical fine pollution aerosols. The comparison of aerosol extinction profiles determined from inelastic-backscatter signals by the Raman method and from elastic-backscatter signals by using the Fernald method with constant value of lidar ratio (50 sr) have shown that reliable aerosol extinction coefficients cannot be determined from elastic-backscatter signals alone, because the lidar ratio varies with aerosol types. A combined Raman and elastic backscatter lidar system can provide reliable information about the aerosol extinction profile and the aerosol lidar ratio.
Keywords
Raman lidar; Elastic lidar; Lidar ratio; Particle extinction; Dust and pollution aerosols;
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