Optical properties of desert aerosol –II–

The optical parameters of the desert aerosol at six sites representative of the desert zones: Oujda and Ouarzazate (Morocco, North Africa), Tamanrasset (Algeria, North Africa), Birdsville (Australia), Dalanzadgad (Mongolia, Asia) and Frenchman-Flat (Nevada, West of United States) are determined. The particle size distributions is near 0.145 μm for the fine particles and 2.06 μm for the coarse ones. The largest volume concentration recorded at Tamanrasset (0.271μm^3/μm^2), due mainly to the coarse particles mode (0.255 μm^3/μm^2) in agreement with the Angstrom coefficients of the order of 0.2. Birdsville and Frenchman-Flat registred the lowest concentrations of the order of 0.030 μm^3/μm^2. The asymmetry factor has a high regularity around 0.65 for fine particles and 0.90 for coarse particles. The diversity of the desert origin shows some variation of the real part of the refractive index of 1.564 (Birdsville) at 1.643 (Frenchman-Flat) and the imaginary part of 13.10^-3 (Tamanrasset) at 157.10^-3 (Birdsville).