A multi-faceted evaluation of aerosol impacts on Arctic clouds

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The project will utilize results from several Arctic measurement sites, including long-term observations at Barrow, Alaska, and shorter-term observations from Summit, Greenland, and two measurement campaigns over the Arctic Ocean to improve upon previous estimates of Arctic aerosol-cloud interactions. To do this a critical first step will involve understanding the conditions under which surface aerosol conditions, as generally used in the compilation of statistical datasets addressing this issue, are comparable to those at cloud level. Using a variety of techniques, the distinction between surface-coupled and decoupled cloud states will focus evaluation of aerosol-cloud interactions on appropriate cases, reducing statistical contamination. From these cases, a statistical evaluation will be performed to reveal co-variation between key cloud (e.g. liquid water path, ice water path) and aerosol (e.g. concentration, size, hygroscopicity) properties. Combined with surface radiation measurements and idealized radiative transfer simulations, the results from this evaluation will provide an improved estimate of the net radiative impact of aerosols on Arctic clouds. Additionally, it will provide an overview of the seasonal evolution and surface-state dependence of these relationships. Outreach plans include several visits to Arctic regions, with a focus on the North Slope of Alaska and Greenland. The primary aim of these visits is to disseminate information relevant to the proposed research to seminar audiences consisting of local people (including underrepresented native people), primary school students, and local officials. A secondary aim of these visits is to give Arctic researchers (particularly early career researchers) who have never had a chance to visit the Arctic themselves an opportunity to see firsthand the region on which their efforts focus. This project will also support two early career scientists at the University of Colorado.