HR: 17:15h
AN: A24B-06    [Abstracts]
TI: Might anthropogenic aerosol be stimulating Arctic sea ice melting through their effects on clouds?
AU: Zhao, C
EM: czhao@lbl.gov
AF: University of Utah, 135 S 1460 E Rm 819, Salt Lake City, UT 84112, United States
AU: * Garrett, T
EM: tim.garrett@utah.edu
AF: University of Utah, 135 S 1460 E Rm 819, Salt Lake City, UT 84112, United States
AU: Maestas, M
EM: honeybeecamping@aim.com
AF: University of Utah, 135 S 1460 E Rm 819, Salt Lake City, UT 84112, United States
AB: It has recently been shown that aerosol have the capacity to increase low cloud longwave emissivity in the Arctic. Aerosols are most abundant in the Arctic during winter and spring, when any increased thermal emission by clouds is likely to augment the rate of seasonal sea-ice melt.Aerosol also indirectly cools the Arctic surface in summer, provided it is black, and the sea-ice or snow have melted. However, averaged over the year, the net indirect forcing of the surface is strongly positive. Measurements at Barrow indicate that polluted clouds emit 10 to 15 W/m2 more longwave radiation than clean clouds. Notably, the magnitude of the effect appears to be influenced not only by increased density of droplet absorption cross-sections, but also by aerosol-cloud-radiation interactions. We demonstrate numerical simulations that illustrate how pollution amplifies cloud-top radiative cooling, and that this translates to more substantial, and more highly radiative, Arctic stratus.
DE: 0321 Cloud/radiation interaction
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting