Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

摘要

We present our combined Raman/elastic backscatter lidar observations whichwere carried out at the EARLINET station of Thessaloniki, Greece, during theperiod 2001–2007. The largest optical depths are observed for Saharan dustand smoke aerosol particles. For local and continental polluted aerosols themeasurements indicate high aerosol loads. However, measurements associatedwith the local path indicate enhanced aerosol load within the PlanetaryBoundary Layer. The lowest value of aerosol optical depth is observed forcontinental aerosols, from West directions with less free troposphericcontribution. The largest lidar ratios, of the order of 70 sr, are found forbiomass burning aerosols. A significant and distinct correlation betweenlidar ratio and backscatter related ?ngstr?m exponent values wereestimated for different aerosol categories. Scatter plot between lidar ratiovalues and ?ngstr?m exponent values for local and continentalpolluted aerosols does not show a significant correlation, with a largevariation in both parameters possibly due to variable absorptioncharacteristics of these aerosols. Finally for continental aerosols withwest and northwest directions that follow downward movement when arriving atour site constantly low lidar ratios almost independent of size are found.