Story posted April 24, 2013
Event date(s): April 01, 2013 — April 30, 2013
Friday, April 26 12:30-1:30
Room 315, Searles Science Building
Open to the Public
Reception 12:00 pm to 12:30 pm in Searles 314
Aaron Donohoe, as part of the Program in Atmospheres, Oceans and Climate at MIT, explores the processes controlling the global mean energy balance of the Earth and the poleward energy transport in the climate system. The global mean planetary albedo is partitioned into a component due to atmospheric reflection (clouds) and a component due to surface reflection. In the global mean, the vast majority (88%) of the planetary albedo is due to atmospheric processes. The surface makes a substantially smaller contribution to the planetary albedo because atmospheric absorption and reflection of incident radiation attenuate the surface's contribution to planetary albedo by a factor of three. In global climate models, the absorbed shortwave radiation differs by 10 W m-2 due to differences in cloud reflection.
The poleward energy transport in the climate system also differs by approximately 20% in global climate models. We partition the poleward energy transport into components due to emitted longwave radiation, incident shortwave radiation, and the spatial structure in planetary albedo due to atmospheric and surface reflection. We find that inter-model differences in poleward energy transport are primarily a consequence of differences in cloud reflection. These results collectively suggest that the global mean energy balance and the strength of the atmospheric circulation in climate models hinge critically on their representation of clouds.