Aerosols are airborne solid and liquid particles with diameters between 0.001 and 100 micrometers. They remain in the troposphere for the relatively short time of a few days to a few weeks, so their global distribution varies considerably. Aerosols directly influence the earth’s radiation balance by reflecting some of the sunlight back into space. But aerosol particles with dark surfaces (like soot) can also absorb visible light and store it as heat in the lower atmosphere. Aerosols also have an indirect effect as condensation nuclei for droplet formation. Depending on particle properties, they can influence cloud formation and characteristics (brightness, lifetime). They can also affect the regional water cycle.
Understanding of global aerosol distribution, its composition and climate effects is still quite incomplete. At DFD new retrieval methods are being developed for remotely sensing aerosols and their characteristics from space, and the results are validated by comparison with ground measurements before they are processed for incorporation in atmosphere models. A new synergetic method (SYNAER) has been used since 2003 to monitor aerosol optical density (a value for the optically relevant total amount of aerosols) and to describe the content of ground-level aerosol mixtures containing various types of particles (secondary aerosols, sea salt, soot, mineral dust). It analyzes the data from two simultaneously measuring sensors on the European environmental satellite ENVISAT: SCIAMACHY and AATSR. Furthermore, data from the geostationary MSG platform are being used to derive a bitemporal dust index, which will make possible regular monitoring of bright desert areas in particular.