A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula
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Abstract© 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.
CitationMasmoudi M, Alfaro SC, El Metwally M (2015) A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula. Atmospheric Research 158-159: 24–35. Available: http://dx.doi.org/10.1016/j.atmosres.2015.02.005.
SponsorsAll the data used in this work are available online at (http://aeronet.gsfc.nasa.gov/new_web/data.html). The authors would like to thank the PIs and site managers of the Masdar (P. Armstrong), KAUST Campus (G.L. Stenchikov), Solar Village (B. Holben), Cairo (M. Korany), Sede Boker (A. Karnieli), Oujda (M. Diouri), La Laguna (F.J. Exposito and J.P. Diaz), Tamanrasset (E. Cuevas), Zinder (M. A. Saley, M. Mahamadou, B. Chatenet, J.L. Rajot, and A. Feron), Banizoumbou (A. Maman, A.Zakou, and D Tanré), Cinzana (M.Coulibaly, I. Koné, and B. Chatenet), Dakar (A. Diallo, T. NDiaye, D. Tanré), and Cabo Verde (F. Evora, D. Tanré) stations for their efforts in maintaining them.They are also grateful to the AERONET/NASA teams for processing the sunphotometers’ data, making the data available and calibrating some of the instruments. The others have been calibrated within AERONET-EUROPE TNA supported by PHOTONS/AERONET (INSU/CNRS) and RIMA network and partially financed by the European Community - Research Infrastructure Action under the Seventh Framework Programme (FP7/2007–2013) “Capacities” specific programme for Integrating Activities, ACTRIS Grant Agreement no. 262254.This study is a contribution to the DGRST/CNRS COMMODEK projet #13R 1001 and to the AIRD/STDF(#5404) SUSIE project.