Characterizing aerosols and their effect on clouds

Abstract

Aerosols are omnipresent in the Earth’s atmosphere but show a large variability in their temporal and spatial distribution. They impact the Earth’s radiation budget by scattering and absorbing incoming and outgoing radiation, and by changing cloud formation and cloud properties and with this, the radiative effects of these clouds. Overall, aerosols are estimated to have a negative effective radiative forcing, meaning a cooling effect. But their impact strongly depends on their location and on their microphysical properties. Specific aerosols (e.g. black carbon) can also have a positive radiative forcing. In addition, different aerosol types interact differently with clouds. Thus, it is important to first correctly identify the aerosol type and then in a second step to study the interaction of each specific type with clouds. Only in this way it will be possible to reduce the large uncertainties in our knowledge about the Earth’s radiation budget which are linked to aerosols and clouds.