For the first time, a dense data set of particle extinction-to-backscatter ratios (lidar ratios), linear depolarization ratios, and backscatter- and extinction-related ?ngstr?m exponents for a Central Asian site are presented. The observations were performed with a continuously running multiwavelength polarization Raman lidar at Dushanbe, Tajikistan, during an 18-month campaign (March?2015 to August?2016). The presented seasonally resolved observations fill an important gap in the database of aerosol optical properties used in aerosol typing efforts with spaceborne lidars and ground-based lidar networks. Lidar ratios and depolarization ratios are also basic input parameters in spaceborne lidar data analyses and in efforts to harmonize long-term observations with different space lidar systems operated at either 355 or 532nm. As a general result, the found optical properties reflect the large range of occurring aerosol mixtures consisting of long-range-transported dust (from the Middle East and the Sahara), regional desert, soil, and salt dust, and anthropogenic pollution. The full range from highly polluted to pure dust situations could be observed. Typical dust depolarization ratios of 0.23–0.29 (355nm) and 0.30–0.35 (532nm) were observed. In contrast, comparably low lidar ratios were found. Dust lidar ratios at 532nm accumulated around 35–40sr and were even lower for regional background dust conditions (20–30sr). Detailed correlation studies (e.g., lidar ratio vs. depolarization ratios, ?ngstr?m exponent vs. lidar ratio and vs. depolarization ratio) are presented to illuminate the complex relationships between the observed optical properties and to identify the contributions of anthropogenic haze, dust, and background aerosol to the overall aerosol mixtures found within the 18-month campaign. The observation of 532nm lidar ratios (25sr) and depolarization ratios (around 15%–20%) in layers with very low particle extinction coefficient (30sr) suggests that direct emission and emission of resuspended salt dust (initially originated from numerous desiccating lakes and the Aralkum desert) have a sensitive impact on the aerosol background optical properties over Dushanbe.
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