HR: 0800h
AN: C31A-0303    [Abstracts]
TI: A spatially explicit snow model in a mid-latitude alpine basin
AU: * Colee, M
EM: mtc@bren.ucsb.edu
AF: University of California, Bren School of Environmental Science & Management, Santa Barbara, CA 93106-5131 United States
AU: Dozier, J
EM: dozier@bren.ucsb.edu
AF: University of California, Bren School of Environmental Science & Management, Santa Barbara, CA 93106-5131 United States
AU: Painter, T H
EM: tpainter@nsidc.org
AF: University of Colorado, CIRES, Boulder, CO 80309 United States
AU: Molotch, N H
EM: molotch@cires.colorado.edu
AF: University of Colorado, CIRES, Boulder, CO 80309 United States
AB: The snowpack in an alpine basin in the Sierra Nevada is analyzed with a spatially-explicit snowmelt model. The 1900 hectare basin lies almost entirely above timberline. We run CRREL's point snow model SNTHERM.89 in each spatial element of a 30 m grid. Three field campaigns during the ablation season obtained depth, density, and temperature measurements for estimating the distribution of snow water equivalent and thermal properties of the snow. Nine remotely sensed images of subpixel snow-covered area provide initialization, validation, and re-initialization. SNTHERM.89 uses grain size retrieved by remote sensing to calculate snow albedo. The initial snow water equivalent image was derived from the first gridded field survey of 429 depth and 33 density samples. We distribute meteorological data at hourly time steps from three stations within the basin to the elevation grid based on calculated lapse rates with elevation. Shortwave radiation inputs to the model are calculated with a topographic radiation model and adjusted for cloud cover based on measured solar radiation. Longwave radiation inputs are calculated with a model incorporating air temperature and relative humidity, with corrections for cloud cover. We validate the model's calculation of the snow cover by comparing snow-covered area, snow water equivalent, and grain size with remote sensing data and field measurements, and we also compared the model snowmelt flux with the hydrograph measured at the basin outlet. Model results are sensitive to correct estimation of albedo. Overall the model matches the hydrograph well, except it misses the very beginning of runoff in the stream. This error is perhaps caused by lateral flow within the snowpack.
UR: http://www.snow.ucsb.edu
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting