ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-17-2011 Seven years of measurements of aerosol scattering properties, near the surface, in the southwestern Iberia Peninsula Pereira S. N. 1 Wagner F. 1 Silva A. M. 1 2 Évora Geophysics Centre, Évora, Portugal Physics Department of the University of Évora, Évora, Portugal 03 01 2011 11 1 17 29 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/17/2011/acp-11-17-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/17/2011/acp-11-17-2011.pdf

Aerosol scattering properties, near the surface (at about 10 m height), were measured during a period of seven years (2002–2008) at Évora, Portugal. The average (and median) scattering and backscattering coefficients, at the wavelength of 550 nm, were found to be 42.5 Mm<sup>−1</sup> (29.9 Mm<sup>−1</sup>) and 5.9 Mm<sup>−1</sup> (4.4 Mm<sup>−1</sup>), respectively. Also, the average and median scattering Ångström exponent (1.4 and 1.5) indicate that scattering was, in general, dominated by sub-micrometer particles. Both seasonal and daily cycles are shown, which were related to local production and transport of particles from elsewhere. Summer and winter average values of the scattering coefficient, at the wavelength of 550 nm (47 and 54 Mm<sup>−1</sup>, respectively), correspond to a significant increase in the aerosol particle concentration when compared with spring and fall (35 and 37 Mm<sup>−1</sup>, respectively). Also, the average increase in the Ångström exponent for summer and winter seasons is consistent with the input of sub-micrometer particles from anthropogenic origin in winter and forest fires in summer. <br><br> Back-trajectory analysis indicated that the site was regularly under the influence of air masses from the Atlantic area, with low particle loads (low scattering coefficients), but as the influence of transport from the continent (Iberia Peninsula) increased, the aerosol particle load was observed to increase as well as the relative importance of fine particles over coarse ones, approaching the features observed at the site during European air masses influence.

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