What are the effects of aerosols?
Aerosols have an important influence on the atmospheric chemistry and physics:
- they affect the atmospheric chemical composition
- they can reduce visibility
- they have important impacts on air quality and human health (e.g. aerosols can cause breathing problems)
- they serve as nuclei for cloud droplets or ice crystals in ice clouds
- they influence the earth's radiation budget in a direct, semi-direct and indirect manner. The scattering and absorption of short and long wave radiation is called the direct effect. This can lead to either warming or cooling of the atmosphere depending on the proportion of light scattered to that absorbed. The semi-direct effect describes the warming of the boundary layer, through the absorption of radiation by aerosols, which can lead to evaporation of clouds. This will allow more solar radiation to reach the surface. The indirect effect concerns the ability of aerosols to act as cloud condensation nuclei which influences the micro-physical and optical properties of clouds, thus changing the radiative and precipitation properties and the lifetime of clouds.
Because of a lack of information concerning the temporal and spatial distribution of aerosols, they are key contributors to the uncertainties in current climate studies.