Aerosol particles modify the transfer of solar radiation in the atmosphere. To quantify
this impact, the composition and the size distribution of the aerosol have to be known.
Simulations with the comprehensive model system KAMM/DRAIS including
meteorological processes, gas phase chemistry and aerosol dynamics and chemistry were
carried out to investigate the impact of aerosol particles on global radiation.
The model system is applied to a summer situation in the southwestern part of Germany.
The aerosol model (MADEsoot) follows the modal approach and represents the aerosol
population by several overlapping modes and accounts of the species sulfate, nitrate,
ammonium, soot and water. Since the optical properties of soot particles depend critically
on their mixing state, the transfer of soot from the external into the internal mixture is
parameterized. Based on the simulated aerosol distributions the optical properties of the
aerosol were derived using Mie calculations. These results serve as input data for the
radiative transfer calculations. It is shown that the for the presented summer situation the
aerosol in the boundary layer reduces the downward flux of the solar radiation by up to
28 W m-2. Sensitivity studies showed that up to 50 % of this effect can be attributed to the
impact of soot.
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