Aerosols are particles in the solid or liquid phase that are suspended in the atmosphere. They have an important influence on the atmospheric chemistry and physics, affect the tropospheric chemical composition, can reduce visibility and have important impacts on human health. Aerosols also influence the Earth’s radiation budget. Although a lot of research has been done to investigate the influence of aerosols on the climate, they remain key contributors to the uncertainties in current climate studies due to the lack of information concerning their temporal and spatial distribution. One of the parameters that is of importance to understand the influence of aerosols is the aerosol optical depth (AOD), an integral measurement of the combined aerosol scattering and absorption in the atmospheric column. The first part of this PhD describes an adapted and improved method for the retrieval of AOD values using sun scan measurements from a Brewer spectrophotometer at 340 nm at Uccle. The retrieved AOD values are subjected to a cloud screening technique and are compared to quasi simultaneous, collocated CIMEL AOD values. The good agreement between both instruments highlights that the Brewer is largely sensitive to AOD at 340 nm and it justifies its use in sun scan mode to expand the AOD retrieval network of instruments. The monthly and seasonal behavior of the retrieved AOD values is also studied in this work and our results agree with results found in literature.Another point of concern in scientific communities is the known adverse effect of UV radiation on human health, the biosphere and atmospheric chemistry. Apart from its obvious relation with global solar radiation and ozone, the amount of UV radiation that reaches the surface of the Earth also depends on the characteristics and quantity of aerosols in the atmosphere and accuracy in UV prediction can be improved if the influence of aerosols on surface UV radiation is clarified. For this reason, the second part of this work focuses on the relation between the ...