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MISU Research Seminar | Cheng You

A Satellite Perspective of Summer Warm-air Advection over Melting Sea Ice

by Cheng You
PhD student at the Department of Meteorology (MISU)

Time: 6 December 2018, 14h15–15h15
Venue: Rossbysalen C609, Arrhenius Laboratory, 6th floor

Abstract
Some very special conditions apply in summer warm-air intrusions as compared to in winter. As long as significant melting sea ice is present, surface temperature must remain at the melting point, in contrast to winter when the surface temperature can respond to changes in the heat surface fluxes. Strong surface inversion forms often accompanied by fog and the high temperature of the fog and its large longwave emissivity brings positive net longwave surface radiation, while the inversion conditions bring a downward turbulent heat flux. Studies based on data from the 2014 Arctic Clouds in Summer Experiment (ACSE), on the Swedish icebreaker Oden, indicate that while low clouds and fog reduce the net solar radiation at the surface, the combined effect on all terms in the surface energy budget leads to additional heat flux to the surface in these conditions; the net outgoing longwave radiation at the top of the atmosphere also increases. We hypothesize that cloud-top cooling and cloud-induced along with surface mixing eventually erodes the surface inversion downstream and the boundary layer transforms into the often-observed well-mixed cloud-capped boundary layer; the extra surface energy is concentrated to a zone inside the ice edge. To evaluate the hypothesis, and to determine the time/length scales involved in the transition, we use a combination of reanalysis, back trajectories and satellite products to extend the view from the local column observations from the icebreaker.

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