Articles | Volume 27, issue 7
Ann. Geophys., 27, 2903–2912, 2009

Special issue: From Deserts to Monsoons – First International Aegean...

Ann. Geophys., 27, 2903–2912, 2009

  22 Jul 2009

22 Jul 2009

Dust specific extinction cross-sections over the Eastern Mediterranean using the BSC-DREAM model and sun photometer data: the case of urban environments

E. Gerasopoulos1, P. Kokkalis2, V. Amiridis3, E. Liakakou1, C. Perez4, K. Haustein4, K. Eleftheratos5,6, M. O. Andreae7, T. W. Andreae7, and C. S. Zerefos5,6 E. Gerasopoulos et al.
  • 1Institute for Environmental Research and Sustainable Development, National Observatory of Athens, I. Metaxa & V. Pavlou, 15236, P. Penteli, Athens, Greece
  • 2National Technical University of Athens, Physics Department, Athens, Greece
  • 3Institute for Space Applications and Remote Sensing, National Observatory of Athens, I. Metaxa & V. Pavlou, 15236, P. Penteli, Athens, Greece
  • 4Earth Sciences Division, Barcelona Supercomputing Center, Barcelona, Spain
  • 5National Kapodistrian University of Athens, Geology Department, Athens, Greece
  • 6Biomedical Research Foundation, Academy of Athens, Athens, Greece
  • 7Biogeochemistry Department, Max Planck Institute for Chemistry, 55020 Mainz, Germany

Abstract. In this study, aerosol optical depth (AOD) measurements, from a MFR sun photometer operating in Athens, were compared with columnar dust loading estimations, from the BSC-DREAM model, during identified dust events, in order to extract the typical specific extinction cross-section for dust over the area. The selected urban environment of Athens provided us with the opportunity to investigate the mixing of dust and urban pollution and to estimate the contribution of the latter. The specific extinction cross-section for dust at 500 nm was found to be equal to σ500*=0.64±0.04 m2 g, typical for medium to large distances from dust sources, with weak wavelength dependence in the visible and near infrared band (0.4–0.9 μm). The model showed a tendency to underpredict AOD levels for increasing values of the Ångström exponent, indicative of fine particles of anthropogenic origin inside the boundary layer. On average we found an AOD under-prediction of 10–15% for Ångström exponents in the range of 0 to 1 and 30–40% in the range of 1 to 2. Additionally, modelled surface concentrations were evaluated against surface PM10 measurements. Model values were lower than measured surface concentrations by 30% which, in conjunction with large scatter, indicated that the effect of the boundary layer anthropogenic contribution to columnar dust loadings is amplified near the ground.