ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-3359-2011 Space-based evaluation of interactions between aerosols and low-level Arctic clouds during the Spring and Summer of 2008 Tietze K. 1 4 Riedi J. 2 Stohl A. 3 Garrett T. J. 1 Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, USA Laboratoire d'Optique Atmosphérique, Université de Lille1/CNRS, France Norwegian Institute for Air Research, Kjeller, Norway deceased 08 04 2011 11 7 3359 3373 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/3359/2011/acp-11-3359-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/3359/2011/acp-11-3359-2011.pdf

This study explores the indirect effects of anthropogenic and biomass burning aerosols on Arctic clouds by co-locating a combination of MODIS and POLDER cloud products with output from the FLEXPART tracer transport model. During the activities of the International Polar Year for the Spring and Summer of 2008, we find a high sensitivity of Arctic cloud radiative properties to both anthropogenic and biomass burning pollution plumes, particularly at air temperatures near freezing or potential temperatures near 286 K. However, the sensitivity is much lower at both colder and warmer temperatures, possibly due to increases in the wet and dry scavenging of cloud condensation nuclei: the pollution plumes remain but the component that influences Arctic clouds has been removed along transport pathways. The analysis shows that, independent of local temperature, cloud optical depth is approximately four times more sensitive to changes in pollution levels than is cloud effective radius. This suggests that some form of feedback mechanism amplifies the radiative response of Arctic clouds to pollution through changes in cloud liquid water path.

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