Articles | Volume 9, issue 12
Atmos. Meas. Tech., 9, 5997–6011, 2016
Atmos. Meas. Tech., 9, 5997–6011, 2016

Research article 13 Dec 2016

Research article | 13 Dec 2016

Aerosol absorption retrieval at ultraviolet wavelengths in a complex environment

Stelios Kazadzis1,2, Panagiotis Raptis2, Natalia Kouremeti1, Vassilis Amiridis3, Antti Arola4, Evangelos Gerasopoulos2, and Gregory L. Schuster5 Stelios Kazadzis et al.
  • 1Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center (PMOD/WRC), Dorfstrasse 33, 7260 Davos Dorf, Switzerland
  • 2Institute of Environmental Research and Sustainable Development, National Observatory of Athens, Greece
  • 3Institute of Astronomy Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Greece
  • 4Finnish Meteorological Institute, Kuopio Unit, Finland
  • 5NASA Langley Research Center, Hampton, VA, USA

Abstract. We have used total and diffuse UV irradiance measurements from a multi-filter rotating shadow-band radiometer (UVMFR) in order to investigate aerosol absorption in the UV range for a 5-year period in Athens, Greece. This dataset was used as input to a radiative transfer model and the single scattering albedo (SSA) at 368 and 332 nm was calculated. Retrievals from a collocated CIMEL sun photometer were used to evaluate the products and study the absorption spectral behavior of retrieved SSA values. The UVMFR SSA, together with synchronous, CIMEL-derived retrievals of SSA at 440 nm, had a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) encountered at the shorter wavelengths. In addition, noticeable diurnal variation of the SSA in all wavelengths is shown, with amplitudes up to 0.05. Strong SSA wavelength dependence is revealed for cases of low Ångström exponents, accompanied by a SSA decrease with decreasing extinction optical depth, suggesting varying influence under different aerosol composition. However, part of this dependence for low aerosol optical depths is masked by the enhanced SSA retrieval uncertainty. Dust and brown carbon UV absorbing properties were also investigated to explain seasonal patterns.

Short summary
Aerosols play an important role in the Earth's climate. One of the main aerosol properties is the single scattering albedo which is a measure of the aerosol absorption. In this work we have presented a method to retrieve this aerosol property in the ultraviolet and we presented the results for measurements at the urban environment of Athens, Greece. We show that the spectral dependence of the aerosol absorption in the VIS–IR and the UV range depends on the aerosol composition and type.