Characteristics of the Lidar Ratio Determined from Lidar and Sky Radiometer Measurements in East Asia

We present aerosol lidar ratio (extinction-to-backscatter ratio; the ratio between optical extinction and backscatter), which is an important parameter used in the determination of the aerosol extinction profiles and subsequently the aerosol optical depth (AOD), determined by combining simultaneous elastic-backscatter lidar and sky radiometer measurements in East Asia. In this study, sky radiometer-derived AOD is used as a constraint and the lidar ratio is calculated when the discrepancy of AOD between lidar and sky radiometer is less than 0.5%. The annual mean lidar ratio (with standard deviation) at 532 nm calculated from 4-year measurements of elastic backscatter lidar and sky radiometer in Seoul, Korea, is found to be 61.7×16.5 sr, and weak seasonal variations are noted with a maximum in summer (68.1×16.8 sr) and a minimum in winter (57.2×17.9 sr). The lidar ratios for clean, dust, and polluted conditions are estimated to be 45.0×9.5 sr, 51.7×13.7 sr, and 62.2×13.2 sr, respectively. While the lidar ratio for the polluted condition is appears to be consistent with previous studies (50-70), clean and dust conditions tend to have larger values, compared to previous estimates (clean: 30-40, dust: 40-50). We also calcualte the lidar ratio from simultaneous observations of ground-based lidar and sky radiometer at six locations (Seoul, Gosan, Fukue, Osaka, Chiba, and Tsukuba) during the Distributed Regional Aerosol Gridded Observation Networks (DRAGON) - NE Asia 2012 campaign. The mean lidar ratios are estimated to be 60~70 sr. During the dust event on 27-29 April 2013, the lidar ratio is decreased to 50~60 sr, which is consistent with other previous studies in East Asia (e.g., Catrall et al., JGR, 2005; Liu et al., App. Opt., 2002; Murayama et al., JGR, 2003). Detailed results will be presented.