October 18, 2013


Aerosol optical thickness at 865 nm wavelength for the total size distribution.
Aerosol optical thickness at 865 nm wavelength for the small mode.
Angström exponent.

The main aerosol content is observed on Atlantic Ocean, around the western and south Saharan coast. This large optical thickness are correlated with small (0.4-0.6) Angström exponent, corresponding to large particles. Nevertheless, close to the coast, the important contribution of small particles suggests the presence of biomass burning aerosols.

Small particles often appear close to the continents (Mediterranean Sea; North Australian Coast, China Sea) but specially around Madagascar and India where they are associated with high Angström exponents. These aerosols are generated from biomass burning in South Africa and Madagascar, and from human activities (industry, heating) in India.

Far away from the continents (Central Pacific), the optical thickness of the small particle mode is low (less than 0.02): when the large particle content is also low, the Angström exponent of the mixing is high (about 1.4); on the contrary, the resulting Angström exponent is rather low (0.5).