Description: On 24 March 2007, an extraordinary dust plume was observed in the Central European troposphere. Satellite observations revealed its origins in a dust storm in Southern Ukraine, where large amounts of soil were resuspended from dried-out farmlands at wind gusts up to 30 m s?1. Along the pathway of the plume, maximum particulate matter (PM10) mass concentrations between 200 and 1400 ?g m?3 occurred in Slovakia, the Czech Republic, Poland, and Germany. Over Germany, the dust plume was characterised by a volume extinction coefficient up to 400 Mm?1 and a particle optical depth of 0.71 at wavelength 0.532 ?m. In-situ size distribution measurements as well as the wavelength dependence of light extinction from lidar and Sun photometer measurements confirmed the presence of a coarse particle mode with diameters around 2?3 ?m. Chemical particle analyses suggested a fraction of 75% crustal material in daily average PM10 and up to 85% in the coarser fraction PM10?2.5. Based on the particle characteristics as well as a lack of increased CO and CO2 levels, a significant impact of biomass burning was ruled out. The reasons for the high particle concentrations in the dust plume were twofold: First, dust was transported very rapidly into Central Europe in a boundary layer jet under dry conditions. Second, the dust plume was confined to a relatively stable boundary layer of 1.4?1.8 km height, and could therefore neither expand nor dilute efficiently. Our findings illustrate the capacity of combined in situ and remote sensing measurements to characterise large-scale dust plumes with a variety of aerosol parameters. Although such plumes from Southern Eurasia seem to occur rather infrequently in Central Europe, its unexpected features highlights the need to improve the description of dust emission, transport and transformation processes needs, particularly when facing the possible effects of further anthropogenic desertification and climate change.

Description: For efficient planning and integration of photovoltaic power plants into the power grids, better knowledge of the aerosol-cloud-radiation interaction and more accurate radiation forecasts are needed. However, most operational numerical weather prediction models rely on an aerosol climatology and ignore the spatio-temporal variability of the atmospheric aerosol. In special weather conditions like Saharan dust outbreaks or extended wildfires, this leads to significant deficiencies in the operational forecasts. At Deutscher Wetter­dienst (DWD) and Karlsruhe Institute of Technology (KIT) the project "PermaStrom" aims to improve radiation forecasts. Using the ICON-ART modeling system the emission, transport, and deposition of mineral dust, black carbon from vegetation fires, and sea salt are explicitly simulated. To achieve the project goals and to examine in detail, the effect of Saharan dust on solar radiation, accurate and extensive measurements of the Saharan dust in the atmosphere and of the ground reaching solar radiation is needed. In our presentation, we will show results for several strong dust episodes in Germany. Dust clouds transported from the Saharan region to Germany are detected and tracked using ceilometer, spectroscopic and broadband radiation measurements from several sites within the measurement network of the DWD. We will focus on the direct and indirect aerosol effects and how these affect the solar irradiance at the ground. Furthermore, we will show how the implementation of prognostic mineral dust in the ICON-ART NWP model can improve the radiation forecasts during such events.