HR: 1340h
AN: C23A-0930    [Abstracts]
TI: A handheld device for measuring snow grain size at centimeter resolution using IR- and visible- spectrum sensors
AU: * Fudge, T
EM: tjfudge@u.washington.edu
AF: Earth and Space Sciences Univ. of Washington, Johnson Hall 070, Box 351310, Seattle, WA 98195, United States
AU: Smith, B
EM: ben@ess.washington.edu
AF: Applied Physics Lab Univ. of Washington, 1013 NE 40th Street Box 355640, Seattle, WA 98105, United States
AU: Waddington, E D
EM: edw@ess.washington.edu
AF: Earth and Space Sciences Univ. of Washington, Johnson Hall 070, Box 351310, Seattle, WA 98195, United States
AB: The estimation of snow grain size from multiple-wavelength satellite imagery is well established as a glaciological technique. These techniques use the fact that large-grained snow absorbs strongly in the infrared to obtain grain estimates based on the difference between reflectance of sunlight in the visible spectrum to that in the infrared. Similar techniques hold promise for estimating grain size variations in firn core, in snow-pits and in boreholes. However, reflectance measurements with small light sources and detectors are complicated by the scattering behavior of snow, in which visible-wavelength photons propagate for much longer distances than infrared photons before being absorbed. This means that density variations as well as grain size variations can change the relative reflectances in the visible and infrared spectra. We present modeling and experimental results in the development of a handheld instrument that will allow grain- size measurements to be made at centimeter resolution. This instrument uses multiple visible-light detectors to estimate the spreading distance of visible photons. This gives an estimate of the scattering density, which in turn allows us to correct the infrared-visible spectral differences, giving a robust estimate of grain size. We present monte-carlo modeling of the measurement, validation experiments using laboratory standards, and measurements on firn cores.
DE: 0720 Glaciers
DE: 0724 Ice cores (4932)
DE: 0726 Ice sheets
SC: Cryosphere [C]
MN: 2007 Fall Meeting