HR: 17:00h
AN: B34B-05    [Abstracts]
TI: Radiative effects of desert dust deposits to alpine snow
AU: * Painter, T H
EM: tpainter@nsidc.org
AF: National Snow and Ice Data Center, University of Colorado at Boulder 449 UCB, Boulder, CO 80309 United States
AU: Barrett, A P
EM: apbarret@nsidc.org
AF: National Snow and Ice Data Center, University of Colorado at Boulder 449 UCB, Boulder, CO 80309 United States
AU: Landry, C
EM: clandry@snowstudies.org
AF: Center for Snow and Avalanche Studies, P.O. Box 190, Silverton, CO 81433 United States
AU: Neff, J C
EM: neffjc@colorado.edu
AF: Departments of Geological Sciences and Environmental Studies, University of Colorado at Boulder 399 UCB, Boulder, CO 80309 United States
AB: Winter and spring storms crossing the Colorado Plateau entrain radiatively absorbing dust from the desert regions and redistribute optically thick layers to the snow cover in the San Juan Mountains as wet and dry deposition. Dust loading in the atmosphere decreases the surface irradiance through scattering and absorption. However, dust loading at the snow surface (which persists well beyond the dust storm event) positively forces tropospheric temperatures through direct and indirect effects. Absorption by dust in the snow increases snow temperature, decreasing the column cold content of the snowpack and increasing the energy available for melt. This represents the direct effect of dust deposition on regional radiation. Indirect effects occur as associated increases in snow grain size (further lowering albedo) and the more rapid snowpack ablation that reveals a darker substrate. In the years 2003 to 2005, we have observed 3 to 4 significant dust deposition events per year. The average date of the first dust event of the season over this period was March 18, the average date of all dust events was April 5, and the average date of the last dust deposition on snow was April 28. Dust events came as late as May 11, 2004. Our monitoring of surface radiative fluxes commenced in winter/spring 2005 at an alpine meteorological tower and a subalpine meteorological tower in the San Juan Mountains. Soon after dust deposition events in early April, snow albedo dropped from 0.86 to 0.6 over 9 days, representing a near-tripling of net shortwave radiation. After an early May dust deposition and snowfall, snow albedo again dropped from 0.85 to 0.55 over 8 days and maintained approximately that value for ~ 45 days with transitory increases after small snowfall events. Dust chemistry and mineralogy of dust samples from the snowpack are consistent with origins in the western US. In this work we present analyses of detailed in situ measurements of broadband and spectral shortwave radiation, field measurements of the hyperspectral shortwave radiation, and coupling of the above measurements with remotely sensed multispectral and hyperspectral imagery to estimate the impact of dust deposits on regional radiative processes.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0740 Snowmelt
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 3359 Radiative processes
SC: Biogeosciences [B]
MN: Fall Meeting 2005