Arctic cloud-capped boundary layers
Funding source: Swedish Research Council - Vetenskapsrådet (VR)
Period: 1/1/10 - 12/31/12
Funding: 2228000 SEK
Description:
ASCOS studies Arctic clouds from unique data gathered during an expedition to the central Arctic summer of 2008, onboard the Swedish icebreaker Oden. Low-level clouds are the single-most important factor in controlling the energy balance at the Arctic sea-ice surface, in turn determining the annual melt and freeze of the Arctic perennial sea ice. Arctic low-level clouds are superficially similar to clouds over for example sub-tropical oceans, but at a closer look often behave differently. For example, in the Arctic these clouds are a warming factor for the surface whereas their subtropical cousins are cooling. They develop under different conditions, for example in different atmospheric circulation and in a different aerosol climate; the tiny particles in the atmosphere that are necessary for clouds to form are much more sparse than at lower latitudes and have different formation processes and life cycles. This contributes to making clouds less reflective for solar radiation and more likely to precipitate. The precipitation is often frozen even in liquid water clouds; a form of mixed-phase clouds that are common in the Arctic even at summer temperatures. Such differences compared to mid-latitude or sub-tropic clouds is manifest in an inability of current climate models to simulate these clouds, and thus the surface energy balance, correctly. ASCOS is devoted to understanding Arctic summer clouds to be able to develop adequate descriptions of these for climate models.
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