This paper analyzes aerosols in the Sahelian zone, particularly in Burkina Faso, based on in situ measurements of the AERONET network made from 1999 to 2006. Indeed, we characterize aerosols by studying their optical and microphysical parameters measured on the site of Ouagadougou (12.2° N, 1.4° W). Thus, several types of days were defined based on the daily averages of optical thicknesses observed. Therefore, cases of days with AOT values 1 and possibly beyond 2.5 or 3 are associated with desert dust occurrences confirmed by the Angstrom oefficient(α440-870 0.9) observed mainly in Winter (DJF) and then in Spring (MAM). These huge falls of mineral dust are due to the proximity of this zone with the Sahel, Burkina Faso being particularly located in the Sahel, as clearly shown by the back trajectories of the air masses drawn at 300 m, 1.000 m and 3.000 m of altitude. These wind trajectories reveal the presence of desert aerosols in all periods, with an influence in Summer due to distant transport at high altitude, nearly 3.000 m, in thin dust, whereas in Winter and in Spring, dust is generated by low-level winds from the North and Northeast. However, mixed days corresponding to AOT values ≥ 0.5 and α440-870 ≥ 0.5 are dominated by more scattering fine desert particles mixed with too much thin combustion aerosols. The combustion particles are due to transports from the Southern part of the country to the Gulf of Guinea, mainly in Winter, Spring and Autumn.

Aerosol AERONET HYSPLIT Back-Trajectory Microphysical and Optical properties Ouagadougou