1Norwegian Institute for Air Research, P.box 100, 2027 Kjeller, Norway
2Grupo de Óptica Atmosférica (GOA-UVA), Universidad de Valladolid, Spain
3Department of Geosciences, University of Oslo, Norway
4Center for International Climate and Environmental Research – Oslo, Norway
5Finnish Meteorological Institute, Helsinki, Finland
6ALOMAR/Andøya Rocket Range, Andenes, Norway
7University of Alaska Fairbanks, Fairbanks, USA
8Institute of Physics, National Academy of Sciences, Minsk, Belarus
9National Institute of Polar Research, Tokyo, Japan
10NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Abstract. In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode.
We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. In addition to AOD measurements, we explored lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and Ny-Ålesund. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. Importantly, at Svalbard it is consistency between the AERONET measurements and calculations of single scattering albedo based on aerosol chemical composition. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for the radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation.