Climatological aspects of aerosol optical properties in Northern Greece E. Gerasopoulos1,2, M. O. Andreae2, C. S. Zerefos1, T. W. Andreae2, D. Balis1, P. Formenti3, P. Merlet2, V. Amiridis1, and C. Papastefanou4 1Laboratory of Atmospheric Physics, Physics Department, Aristotle University of Thessaloniki, P.O. Box 149, GR-54124 Thessaloniki, Greece 2Max Planck Institute for Chemistry, Biogeochemistry Department, P.O. Box 3060, D-55020 Mainz, Germany 3Centre of Geophysics of Évora, Universidade de Évora, Rua R. Ramalho, 59, P-7000-532 Evora, Portugal 4Nuclear Physics Department, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
Abstract. Measurements of aerosol optical properties (aerosol optical depth, scattering and
backscattering coefficients) have been conducted at two ground-based sites in Northern
Greece, Ouranoupolis (40° 23' N, 23° 57' E, 170 m a.s.l.) and Thessaloniki
(40° 38' N, 22° 57' E, 80 m a.s.l.), between 1999 and 2002. The frequency distributions of the observed parameters
have revealed the presence of individual modes of high and low values, indicating the influence from different
sources. At both sites, the mean aerosol optical depth at 500 nm was 0.23. Values increase considerably during summer when they remain persistently between
0.3 and 0.5, going up to 0.7-0.8 during specific cases. The mean value of
65±40 Mm-1 of the particle scattering coefficient at 550 nm reflects the impact of continental pollution in the regional
boundary layer. Trajectory analysis has shown that higher values of aerosol optical
depth and the scattering coefficient are found in the east sector (former Soviet Union countries,
eastern Balkan countries), whereas cleaner conditions are found for the NW direction.
The influence of Sahara dust events is clearly reflected in the Ångström exponents. About
45-60% of the observed diurnal variation of the optical properties was attributed to the
growth of aerosols with humidity, while the rest of the variability is in phase with the evolution
of the sea-breeze cell. The contribution of local pollution is estimated to contribute
35±10% to the average aerosol optical depth at the Thessaloniki site during summer. Finally,
the aerosol scale height (aerosol optical depth divided by scattering coefficient) was found to
be related to the height of the boundary layer with values between 0.5-1
km during winter and up to 2.5-3 km during summer.
Citation: Gerasopoulos, E., Andreae, M. O., Zerefos, C. S., Andreae, T. W., Balis, D., Formenti, P., Merlet, P., Amiridis, V., and Papastefanou, C.: Climatological aspects of aerosol optical properties in Northern Greece, Atmos. Chem. Phys., 3, 2025-2041, doi:10.5194/acp-3-2025-2003, 2003.