Aerosol absorption retrieval at ultraviolet wavelengths in a
complex environment
Abstract. We have used total and diffuse UV irradiance measurements with a multi-filter rotating shadow-band radiometer (UVMFR), in order to calculate aerosol absorption properties (Single Scattering Albedo – SSA) in the UV range, for a 5 years period in Athens, Greece. Τhis data set was used as input to a radiative transfer model and the SSA for 368 nm and 332 nm has been calculated. Retrievals from a collocated CIMEL sun-photometer were used to validate the products and study absorption spectral behavior SSA values at these wavelengths. UVMFR SSA together with synchronous,CIMEL-derived, retrievals at 440 nm, show a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) towards lower wavelengths. In addition, noticeable diurnal variations of the SSA in all wavelengths are revealed, with amplitudes in up to 0.05. High SSA wavelength dependence is found for cases of low Ångström exponents and also an SSA decrease with decreasing extinction optical depth, suggesting an effect of the different aerosol composition. Dust and Brown Carbon UV absorbing properties were investigated to understand seasonal variability of the results.