Das Projekt "Investigation of the removal processes of soot particles from the atomsphere" wird vom Umweltbundesamt gefördert und von NOAA Earth System Research Laboratory durchgeführt. During the International Polar Year of 2008, an airborne field campaign called Aerosol, Radiative, and Cloud Processes affecting Arctic Climate (ARCPAC) has been performed in order to improve the understanding of climate relevant processes playing a role in the Arctic. The climate system in the Arctic is seen to be a dynamic and complex system with many potential non-linear feedbacks both in the Arctic a well as in the global climate system. The measurements took place in the Alaskan Arctic using closely coordinated remote sensing and in situ observations from aircraft and ground sites in the vicinity of Barrow. The main focus was to investigate the efficiency of the removal of aerosol particles and particularly of Black Carbon from the atmosphere by deposition to the surface; the deposition of Black Carbon for instance decreases the albedo of the surface. Studying the composition and the origin of the air masses influencing the Arctic air in spring is also of major interest to better understand which compounds can be deposited. In order to assess these removal processes a broad set of aerosol, gas phase and microphysics instrumentation was deployed. The first results showed that the Arctic air at this period has been strongly influenced by biomass burning emissions. The concentrations were found to be comparable to the one in mega cities but with an aerosol composition dominated by the organic fraction and very high fraction of acetonitrile. Some back-trajectory studies (FLEXPART model) have shown that those biomass plumes were originating from Russia, where this year the snow melted early in the season favoring agricultural burning of lands or forest fires. This shows the strong impact of biomass combustion pollutants transported to the Arctic and thus the potential increase of deposition of particles to the surface. Preliminary results show evidence of removal of aerosol and soot from the atmosphere and thus their potential deposition to the surface. Altitude profiles have shown that the removal of particles appeared to be almost inexistent above the inversion layer at 200-300 m asl. Below this inversion layer the pollutant and particularly soot particles are drastically decreasing. This removal seems to be amplified in the area above the sea ice and particularly above open leads (open water cells in the sea ice). Looking in a more detailed analysis at the type of cloud and at the variation and type of air masses encountered should allow to identify characteristic cases in Arctic that could be used to constrain climate models.