On the optical properties of the polluted Athens atmosphere, during May 1995

Using ground-based spectral solar extinction data taken over the Athens atmosphere, reduced (total minus Rayleigh) and aerosol (Angstrom) spectral optical depths of the atmosphere, have been retrieved, under different polluted conditions. The results suggest that the optical depth, on days with relatively low pollution, exhibits slight variation with wavelength denoting that aerosols deplete all wavelengths almost equally. In contrast, under dense pollution, small particles scattering and trace gases absorption, are the dominant processes, resulting in steeper optical depth’s slopes, mainly in the ultraviolet domain. The Angstrom’s parameters β and α were determined through a least-squares fitting method. The turbidity β coefficient always shows a temporal pattern with high values in the morning and afternoon and low values midday.