HR: 0800h
AN: C21A-1056    [Abstracts]
TI: Hyperspectral Analysis of Dust Concentration, Snow Grain Size, and Broadband Albedo of Alpine Snowcover
AU: * Cassidy, M P
EM: cassidym@nsidc.org
AF: National Snow & Ice Data Center, Cooperative Institute for Research in Environmental Sciences, 216 UCB University of Colorado, Boulder, CO 80309 United States
AU: Painter, T H
EM: tpainter@nsidc.org
AF: National Snow & Ice Data Center, Cooperative Institute for Research in Environmental Sciences, 216 UCB University of Colorado, Boulder, CO 80309 United States
AB: Springtime desert dust storms regularly deposit radiatively absorbing dust upon the San Juan Mountains of southwestern Colorado. The dust deposits reduce the albedo of snow in visible wavelengths, accelerate grain metamorphism, and increase grain size. Because the dust increases net visible absorption and increases grain size, likewise increasing near-infrared and shortwave infrared absorption, the radiative effects of desert dust should have significant impacts upon the energy balance of the seasonal snowpack in the San Juan Mountains. The NASA/JPL Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is of sufficient spectral resolution to quantitatively detect the radiative effects of dust upon the grain size and visible albedo of snow. AVIRIS detects upwelling radiance in 224 contiguous spectral channels within the wavelength range of 400-2500 nanometers, and is flown at ~4 km altitude in a Twin Otter aircraft. We analyze AVIRIS data collected over two energy balance monitoring sites in the alpine and subalpine of Red Mountain Pass in the San Juan Mountains of Colorado. These data were collected on May 19 and May 21 of 2004. We used the software Atmospheric Correction Now (ACORN) to atmospherically correct the AVIRIS data to apparent surface reflectance and enhanced the reflectance retrieval with field spectra of a within scene calibration site. The normalized differential dust in snow index (NDDSI) signifies relative dust concentration by quantifying the slope of a dust absorption feature in the spectral reflectance of snow. An inversion technique based on the quantitative relationship between the area of an ice absorption feature at 1.03 �m and its optically equivalent snow grain size is used to derive the spatial distribution of snow grain radii. The relationship between quantitative estimates of relative dust concentration and grain size is direct up to a threshold dust concentration at which the relationship becomes inverse. The absorption by large concentrations of dust appears to contaminate the scaled area of the 1.03 �m ice absorption feature.
DE: 0700 CRYOSPHERE (4540)
DE: 0712 Cryosol
DE: 0736 Snow (1827, 1863)
DE: 0758 Remote sensing
DE: 0764 Energy balance
SC: Cryosphere [C]
MN: Fall Meeting 2005