HR: 09:10h
AN: A31C-05    [Abstracts]
TI: Dirty Snow, Atmospheric Warming, and Climate Feedbacks from Boreal Black Carbon Emissions
AU: * Flanner, M G
EM: mflanner@uci.edu
AF: Earth System Science Department, University of California-Irvine, Croul Hall, Irvine, CA 92697-3100 United States
AU: Zender, C S
EM: zender@uci.edu
AF: Earth System Science Department, University of California-Irvine, Croul Hall, Irvine, CA 92697-3100 United States
AU: Randerson, J T
EM: jranders@uci.edu
AF: Earth System Science Department, University of California-Irvine, Croul Hall, Irvine, CA 92697-3100 United States
AU: Jin, Y
EM: yufang@uci.edu
AF: Earth System Science Department, University of California-Irvine, Croul Hall, Irvine, CA 92697-3100 United States
AB: Black carbon (BC) emitted from boreal fires darkens snow and sea-ice surfaces, increases solar absorption in the atmosphere, and decreases the incident flux at the surface. Although global surface forcing of darkened snow/ice is small relative to atmospheric forcing, the former directly triggers ice-albedo feedback, whereas the latter directly alters the atmospheric lapse rate. This highlights the importance of examining climate feedback strength as well as instantaneous forcings. We used a coupled land-atmosphere GCM (NCAR CAM3) to compare the relative forcings and climate feedbacks of BC emitted from a suite of boreal forest fires over the last decade, accounting for both enhanced snow/ice and atmospheric absorption by BC. The net change in absorbed energy at the surface was about three times greater than the instantaneous surface forcing when BC interactively heated the snow. Timing and location of fires determined the magnitude of darkened snow/ice feedback potential. We also assessed climate feedback strength from BC emitted globally during extreme high and low fire years, including the 1998 fire season.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0360 Radiation: transmission and scattering
DE: 0736 Snow (1827, 1863)
DE: 0750 Sea ice (4540)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005