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The impact of aerosol on clouds and precipitation varies depending on the cloud type. This case study focusses on convective clouds developing after the passage of a frontal system from the North Sea over Germany. In contrast to deep convection, the precipitation amount formed in the postfrontal cummuli is thought to show a systematic sensitivity to the natural and anthropogenic aerosol burden. During the front passage, the preexisting anthropogenic aerosol is replaced to a large extent by seasalt aerosol. To quantify the influence of aerosol on these postfrontal cummuli and their precipitation simulations with a comprehensive online coupled model system are performed. As precipitation reacts sensitive to disturbances of any atmospheric state variable, also simulations with slightly and randomly disturbed temperature fields were performed to contrast these effects with the aerosol effect. [ABSTRACT FROM AUTHOR]

Gas-cleaning technologies used in modern coal-fired power plants cause an unintended nucleation of H2SO4 aerosol droplets during the cleaning process. As a result, high concentrations of ultra-fine aerosol droplets are emitted into the atmosphere. In this study, the impact of these emissions on the atmospheric aerosol distribution, on the cloud condensation nuclei number concentration, and consequently on cloud properties is investigated. Therefore, a sophisticated modeling framework is used combining regional simulations of the atmospheric aerosol distribution and its impact on cloud properties with detailed process simulations of the nucleation during the cleaning process inside the power plant. Furthermore, the simulated aerosol size distributions downwind of the coal-fired power plants are compared with airborne aerosol measurements performed inside the plumes. [ABSTRACT FROM AUTHOR]