Optical porperties of free tropospheric aerosol from multi-wavelength raman lidars over the southern Iberian Peninsula

Abstract

Two cases of free tropospheric aerosol layers observed with multi-wavelength Raman lidars over Évora (Portugal) and Granada (Spain) were investigated. Optical properties, both, columnar and vertically-resolved, of a forest fire smoke plume from North America on 13 June 2011, and of mineral dust layers on 27 June 2011 are presented. The aerosol optical depth and Ångström exponents derived from lidar data were compared to sun photometer measurements. The aerosol optical depth at 355 nm of the free tropospheric smoke layers were about 25 to 30% of the columnar aerosol optical depth found from sun photometer measurements at both sites. The lidar ratio at 355 nm was 46±14 sr and 48±16 sr, over Évora and Granada, espectively. The lidar ratio at 532 nm over Évora was 66±19 sr. The investigation of the dust plume showed larger differences in the aerosol optical properties observed at the two sites. This was due to different transportation paths and intrusion of other aerosol types, namely anthropogenic and marine aerosols.