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The Scientific World Journal
Volume 2014 (2014), Article ID 421838, 11 pages
http://dx.doi.org/10.1155/2014/421838
Research Article

Forest Fire Smoke Layers Observed in the Free Troposphere over Portugal with a Multiwavelength Raman Lidar: Optical and Microphysical Properties

1Évora Geophysics Center, Rua Romão Ramalho 59, 7000 Évora, Portugal
2Andalusian Institute for Earth System Research IISTA-CEAMA, University of Granada, Autonomous Government of Andalusia, Avenida del Mediterráneo s/n, 18006 Granada, Spain
3Centre for Climate and Air Pollution Studies (C-CAPS), National University of Ireland Galway, University Road, Galway, Ireland
4Department of Applied Physics, University of Granada, Fuentenueva s/n, 18071 Granada, Spain
5Deutscher Wetterdienst, Meteorologisches Observatorium Hohenpeißenberg, Germany

Received 19 May 2014; Accepted 19 June 2014; Published 10 July 2014

Academic Editor: Roberto Fraile

Copyright © 2014 Sérgio Nepomuceno Pereira et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Vertically resolved optical and microphysical properties of biomass burning aerosols, measured in 2011 with a multiwavelength Raman lidar, are presented. The transportation time, within 1-2 days (or less), pointed towards the presence of relatively fresh smoke particles over the site. Some strong layers aloft were observed with particle backscatter and extinction coefficients (at 355 nm) greater than 5 Mm−1 sr−1 and close to 300 Mm−1, respectively. The particle intensive optical properties showed features different from the ones reported for aged smoke, but rather consistent with fresh smoke. The Ångström exponents were generally high, mainly above 1.4, indicating a dominating accumulation mode. Weak depolarization values, as shown by the small depolarization ratio of 5% or lower, were measured. Furthermore, the lidar ratio presented no clear wavelength dependency. The inversion of the lidar signals provided a set of microphysical properties including particle effective radius below 0.2 μm, which is less than values previously observed for aged smoke particles. Real and imaginary parts of refractive index of about 1.5-1.6 and 0.02i, respectively, were derived. The single scattering albedo was in the range between 0.85 and 0.93; these last two quantities indicate the nonnegligible absorbing characteristics of the observed particles.