HR: 17:30h
AN: A24B-07    [Abstracts]
TI: Radiative Impact of Boreal Smoke in the Arctic: Observed Versus Modeled
AU: Stone, R S
EM: Robert.Stone@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Stone, R S
EM: Robert.Stone@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: * Anderson, G P
EM: gail.anderson@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: * Anderson, G P
EM: gail.anderson@noaa.gov
AF: AFRL/VS, Hanscom AFB, Bedford, MA 01730, United States
AU: Shettle, E P
EM: shettle@nrl.navy.mil
AF: NRL, Code 7227, Washington, DC 20375-5351, United States
AU: Loukachine, K
EM: Konstantin.Loukachine-1@nasa.gov
AF: NASA/LaRC, Langley Research Center, Hampton, VA 23681, United States
AU: Andrews, E
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Andrews, E
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Dutton, E G
EM: Ellsworth.G.Dutton@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AB: The Arctic climate is modulated, in part, by the presence of aerosols that affect the horizontal and vertical distribution of radiant energy passing through the atmosphere, directly through interactions with solar and terrestrial radiation and indirectly through interactions with cloud particles. During summer 2004 forest fires destroyed vast areas of boreal forest in Alaska and western Canada, releasing smoke into the atmosphere that was dispersed widely. Smoke passing over instrumented field sites near Barrow, Alaska was monitored to determine its physical and optical properties and its impact on the surface radiation balance. Empirical determinations of the direct radiative forcing by the smoke were used to corroborate simulations made using the Moderate Resolution Transmittance radiative transfer code, MODTRAN®5. Radiative forcing varying with solar angle and surface type was evaluated at the surface, at the top of the atmosphere (TOA) and within the intervening atmosphere. The TOA results are used to corroborate retrievals from polar orbiting satellites. Smoke cools the surface while warming those layers in which it resides, increasing atmospheric stability and possibly suppressing cloud formation. TOA forcing is especially sensitive to surface albedo, evidenced in both the model results and satellite retrievals. Cooling to space occurs over dark ocean areas while warming occurs over bright snow and ice covered regions. Surface cooling and corresponding layer heating are the dominant radiative effects of boreal smoke at high northern latitudes. Should the frequency and intensity of boreal fires increase in the future due to climate change, the more persistent presence of smoke in the atmosphere may be manifest as a negative feedback at the surface with variable impact on cloud distributions depending on complicated, competing greenhouse and albedo effects of clouds.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0360 Radiation: transmission and scattering
DE: 1610 Atmosphere (0315, 0325)
DE: 3311 Clouds and aerosols
DE: 3359 Radiative processes
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting