Systematic lidar observations of Saharan dust layers over Athens, Greece in the frame of EARLINET project (2004–2006)

摘要

In this paper we present a statistical analysis on the geometrical andoptical properties of Saharan dust layers observed over Athens, Greece, in athree-year period from 1 January 2004 up to 31 December 2006. Theobservations of the vertical aerosol profile were performed by themulti-wavelength (355-532-1064-387-607 nm) Raman lidar system of theNational Technical University of Athens (NTUA) operated in the city ofAthens (37°98' N, 23°77' E), Greece, in the frame of the EuropeanAerosol Research Lidar Network (EARLINET-ASOS) project. The number of dustevents was greatest in late spring, summer, and early autumn periods. Thiswas evident also by aerosol observations during dust outbreaks obtained fromthe Moderate Resolution Imaging Spectroradiometer (MODIS). In our lidarmeasurements, multiple aerosol dust layers of variable thickness (680–4800 m)were observed. The center of mass of these layers was located inaltitudes between 1600 and 5800 m. However, the mean thickness of the dustlayer typically stayed around 2700 m and the corresponding mean center ofmass was of the order of 2900 m. The top of the dust layer ranged from 2000to 8000 m, with a mean value of the order of 4700 m. MODIS observationsduring dust outbreaks showed that the AOD values at 550 nm ranged between0.3–0.6, while the corresponding Angstr?m exponent (AE) values were ofthe order of 0.5–0.65, indicating the presence of rather large particles.