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Volume 16, issue 11 | Copyright
Atmos. Chem. Phys., 16, 7013-7028, 2016
https://doi.org/10.5194/acp-16-7013-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Jun 2016

Research article | 08 Jun 2016

Retrieval of optical and physical properties of African dust from multiwavelength Raman lidar measurements during the SHADOW campaign in Senegal

I. Veselovskii1,2, P. Goloub3, T. Podvin3, V. Bovchaliuk3, Y. Derimian3, P. Augustin4, M. Fourmentin4, D. Tanre3, M. Korenskiy1,5, D. N. Whiteman6, A. Diallo7, T. Ndiaye7, A. Kolgotin1, and O. Dubovik3 I. Veselovskii et al.
  • 1Physics Instrumentation Center of GPI, Troitsk, Moscow, Russia
  • 2Joint Center for Earth Systems Technology, UMBC, Baltimore, MD, USA
  • 3Laboratoire d'Optique Atmosphérie, Université de Lille-CNRS, 59650, Villeneuve-d'Ascq, France
  • 4Laboratoire de Physico-chimie de l'atmosphère, Université du littoral côte d'Opale, Dunkerque, France
  • 5Far Eastern Federal University, Vladivostok, Russia
  • 6NASA GSFC, Greenbelt, MD, USA
  • 7Institut de Recherche pour le Développement, Dakar, Senegal

Abstract. West Africa and the adjacent oceanic regions are very important locations for studying dust properties and their influence on weather and climate. The SHADOW (study of SaHAran Dust Over West Africa) campaign is performing a multiscale and multilaboratory study of aerosol properties and dynamics using a set of in situ and remote sensing instruments at an observation site located at the IRD (Institute for Research and Development) in Mbour, Senegal (14°N, 17°W). In this paper, we present the results of lidar measurements performed during the first phase of SHADOW (study of SaHAran Dust Over West Africa) which occurred in March–April 2015. The multiwavelength Mie–Raman lidar acquired 3β + 2α + 1δ measurements during this period. This set of measurements has permitted particle-intensive properties, such as extinction and backscattering Ångström exponents (BAE) for 355/532nm wavelengths' corresponding lidar ratios and depolarization ratio at 532nm, to be determined. The mean values of dust lidar ratios during the observation period were about 53sr at both 532 and 355nm, which agrees with the values observed during the SAMUM-1 and SAMUM-2 campaigns held in Morocco and Cabo Verde in 2006 and 2008. The mean value of the particle depolarization ratio at 532nm was 30±4.5%; however, during strong dust episodes this ratio increased to 35±5%, which is also in agreement with the results of the SAMUM campaigns. The backscattering Ångström exponent during the dust episodes decreased to ∼ −0.7, while the extinction Ångström exponent, though negative, was greater than −0.2. Low values of BAE can likely be explained by an increase in the imaginary part of the dust refractive index at 355nm compared to 532nm. The dust extinction and backscattering coefficients at multiple wavelengths were inverted to the particle microphysics using the regularization algorithm and the model of randomly oriented spheroids. The analysis performed has demonstrated that the spectral dependence of the imaginary part of the dust refractive index may significantly influence the inversion results and should be taken into account.

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West Africa and the adjacent oceanic regions are very important locations for studying dust properties and their influence on weather and climate. The SHADOW (study of SaHAran Dust Over West Africa) campaign is performing a multiscale and multilaboratory study of aerosol properties and dynamics using a set of in situ and remote sensing instruments at an observation site located at IRD (Institute for Research and Development) in Mbour, Senegal (14° N, 17° W).
West Africa and the adjacent oceanic regions are very important locations for studying dust...
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