| Summary: | Aerosols play a major rule in global warming thought the direct and indirect aerosol effect. Thus, a better understanding of aerosol related properties and processes is crucial to improve climate models. During April (Kiruna, Sweden) and July (Kangerlussuaq, Greenland) 2008, the POLARCAT project, part of the International Polar Year (IPY), aimed to characterize pollution plumes of different origins as they are transported to the Arctic. Within the frame of POLARCAT the french research aircraft ATR-42 was deployed to measure optical (light scattering and absorption), physical (aerosol size distributions) and chemical aerosol properties as well as trace gas concentrations. With the help of air mass back-trajectories from the Lagrangian particle dispersion model FLEXPART, this study aims particularly on the characterization of the physical and optical properties of pollution plumes aerosol particles transported to Greenland (July campaign) from different origins, such as Siberia or Canada. In a first step, optical measurements of aerosol particle size distributions have been corrected accorded to an automated best estimate of the complex refractive index (k) of measured aerosol particles. This work has been carried out after implementation of the Mie code from Bohren & Huffman, where aerosols scattering and absorption coefficients are calculated for measured size distributions (as a function of k) and subsequently are compared to the measurement of aerosol optical properties (scattering, absorption). Then, in a second step, the retrieved refractive indices have been compared to aerosol chemical composition in order to improve the classification of air masses origins in parallel to trace gas concentrations and back-trajectory studies. Canadian and Siberian biomass burning events as well as American and European pollution observations can be detected over Greenland even though distances from regions lead to rather weak observed aerosol particle concentrations.
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