HR: 0800h
AN: B41D-0225    [Abstracts]
TI: Impact of Desert Dust on Meltrates and Runoff from Mountain Snowpacks
AU: * Barrett, A P
EM: apbarret@kryos.colorado.edu
AF: NSIDC-CIRES University of Colorado, 449 UCB, Boulder, CO 80309 United States
AU: Painter, T H
EM: tpainter@nsidc.org
AF: NSIDC-CIRES University of Colorado, 449 UCB, Boulder, CO 80309 United States
AU: Landry, C
EM: clandry@snowstudies.org
AF: Center for Snow and Avalanche Studies, PO Box 190, Silverton, CO 81433 United States
AB: Dust, entrained from desert regions of the Colorado Plateau, is deposited over large areas of the mountain snow pack of the San Juan Mountains, Southwest Colorado. Anecdotal evidence from avalanche forecasters, backcountry rangers and Ute tribal representatives suggests that extensive dust layers occur in most years. Multiple dust layers were found in snowpacks in this region in 2003, 2004 and 2005. Dust, exposed at the snow surface, decreases albedo and increases absorption of solar radiation of the snowpack. In the 2004-2005 snow accumulation and melt season, measurements of surface energy fluxes, snow temperature and snow water equivalent were made at two meteorological towers in the Senator Beck Study Basin, San Juan Mountains, to examine the impact of dust on snowmelt processes. Stream stage at four sites within the basin and at the basin outflow point was also measured to investigate the impact of dust integrated to the basin scale. Dust was first exposed on April 13 but was covered by snowfall on April 23. Dust was exposed again on May 5. Before dust was exposed at the snow surface, broadband albedo at the two towers was between 0.7 and 0.9. After exposure of dust, albedo fell to 0.6. Shortwave radiative fluxes increased from 100 W m-2 to 400 W m-2 over 10 days as a result of dust exposure in April; and increased from 100 W m-2 to 500 W m-2 over 25 days in May. Dust exposure in April coincided with an increase in snowpack temperature in the top layers, a proxy for snowpack internal energy within these layers, from -5C to 0C. In May, dust exposure coincided with an increase in stream stage. Exposure of dust at the snow surface enhanced the role of shortwave radiative fluxes in both ripening the snowpack and in runoff generation.
DE: 1804 Catchment
DE: 1809 Desertification
DE: 1839 Hydrologic scaling
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
DE: 1878 Water/energy interactions (0495)
SC: Biogeosciences [B]
MN: Fall Meeting 2005