The climate of the Arctic is changing rapidly for reasons that are poorly understood. It is generally recognized that low-level cloud cover is a controlling factor in any feedbacks that amplify the rate of change. However, any assessment of the relevant mechanisms at play requires accurate long-term statistical representations of Arctic cloud properties and variability. Past efforts used long-term seasonal data to quantify indirect aerosol amplification to Arctic surface warming: thermal insulation of the surface by low-level Arctic stratus is increased in the presence of mid-latitude aerosol pollution. This new effort aims to expand our understanding of this phenomenon, and Arctic clouds in general, by analyzing long-term data sets collected at the Department of Energy North Slope of Alaska - Adjacent Arctic Ocean, and National Oceanic and Atmospheric Administration, long-term monitoring sites near Barrow, Alaska. Activities will include a) development of new, and refinements to existing, remote-sensing cloud retrieval algorithms for application to Arctic studies; b) derivation of long-term seasonal databases of pollution, low-cloud microstructures, phase, precipitation, and radiative properties, and c) isolation of the component mechanisms that control cloud, aerosol and precipitation interactions in the Arctic. These efforts will result in a deepened understanding of the response of Arctic haze phenomena to a projected warmer, wetter Arctic. The broader impacts of this study are development of new techniques for studying Arctic climate and component processes, web-based dissemination of results of analysis of changing cloud conditions in the Arctic, collaborations between different government agencies and university researchers, undergraduate and graduate student training, and contribution to the broad goals of the 2007 to 2008 International Polar Year.
