| Summary: | A paucity of observations in the Arctic means that neither the aerosol processes nor cloud properties are well understood or represented within models, with the result that aerosol and cloud-forcing of Arctic climate is poorly constrained.Research investigating the lower atmosphere of the arctic has found that low cloud dominates the variability in arctic cloud cover. Temperature and humidity profiles show a high frequency of one or more temperature inversions and below these inversions stratus or stratocumulus clouds form. During the arctic summer these low clouds often consist of multiple layers, with a number of theories describing the separation of these clouds. These clouds have been observed during different seasons but the association between temperature and the formation of ice in these clouds is not well understood. Jayaweera and Ohtake (1973) found that the cloud microphysics consisted of very little ice above -20° but Curry et al., (1996) observed ice clouds at temperatures as high as -14°. It is possible that the variation in temperatures at which point glaciated clouds are observed is caused by variation in the number concentration and composition of aerosol.MethodologyACCACIA measurement campaigns took place during March-April 2012 and July 2012, in the region between Greenland and Norway. Measurements were made from both ship and aircraft platforms. Results presented here will be confined to those from aircraft which made most of their measurements in the regions around and to the south of the Svalbard archipelago. Two aircraft (the FAAM BAe 146 based in Kiruna Sweden, and the British Antarctic Survey (BAS) Twin Otter, based at Lonyearbyan Svalbard) flew during the late winter campaign while only one (the BAS Twin other) flew during the summer period. The overarching theme of the project is to reduce the large uncertainty in the effects of aerosols and clouds on the Arctic surface energy balance and climate. Key to the work presented here is the understanding the microphysical properties of Arctic ...
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