Comparison of in situ and landsat derived reflectance of Alaskan Glaciers

Abstract

Calculation of snow and ice albedo is necessary for developing physically realistic simulations of the Earth's climate using general circulation models, and useful for analysis of glacier mass balance change using remote sensing. Reflectances calculated from TM data and corrected for atmospheric effects correspond with in situ measured reflectances in the nadir-viewing mode, and are shown to be related to a glacier's mass balance if measured over a period of years. A reflectance of 0.895 for a test site in the Wrangell Mountains, Alaska, was calculated from TM Band 4 (0.76–0.90 μm) data and corrected for atmospheric effects. This value was comparable to the in situ reflectance of 0.90 measured in the same 0.76–0.90 μm wavelength region. For the same site, a reflectance value of 0.79 derived from integrating over most (0.40–3.0 μm) of the reflective portion of the electromagnetic spectrum was quite different from the integrated reflectance of 0.95 calculated for the spectral range 0.40–1.0 μm. This demonstrates the importance of using the full reflective energy spectrum for calculating the albedo of snow, and for obtaining a meaningful computation of a glacier's energy and mass balance change.