Detection of the Arctic Dehydration-Greenhouse Feedback

Recent observations have shown that the Arctic warming trend predicted by climate models based mostly on the greenhouse effect is not realized during winter, possibly due to an aerosol-induced counteraction. During the cold season, this aerosol effect includes the dehydration-greenhouse feedback (DGF), a mechanism associated to the long-range transport of anthropogenic sulfur dioxide and sulfates into the Arctic. Sulfuric acid, an end-product of atmospheric sulfur oxidation, covers practically all other aerosols and, by reducing the homogeneous freezing temperature, favorizes the predominance of precipitating diamond dust over ice fog. The consequent acceleration in the dehydration of air masses as they enter the Arctic is accompanied by a reduction in the water content greenhouse effect, and the subsequent surface cooling, by propagating to the boundary layer, promotes further dehydration. This feedback mechanism, whose numerical simulations have revealed the potential to be of climatological significance, may be detected using new satellite data. In this paper, we present the correlation between the humidity field and sulfate concentrations during December 2004 over the Kara Sea, using AIRS data and the NARCM regional model. This work on the detection of the DGF is about to be complemented by data from the CloudSat/CALIPSO mission, which will provide, for the first time, simultaneous profiles of the aerosol and ice crystal fields.