Airborne bidirectional radiances of snow-covered surfaces in Montana, U.S.A.

Abstract

Bidirectional radiance measurements of various snow-covered surfaces have been acquired using the Advanced Solid-State Array Spectro-radiometer (ASAS) which was flown on the NASA C-130 aricraft over Glacier National Park, Montana on 14 March 1991. A frozen lake, a snow-covered meadow, a mixed coniferous/deciduous forest and a dense coniferous forest were studied. Knowledge of the bidirectional reflectance characteristics of various snow-covered surfaces is key to calculation of albedo from satellite sensors in the future. While the reflectance characteristics of pure snow targets have been measured from the ground, aircraft and satellites, very few bidirectional reflectance data exist for surface covers of mixed snow and vegetation. Analysis of the 14 March 1991 ASAS data show that the anisotropic reflectance of snow was strong over the snow-covered frozen lake but slightly dampened over the meadow because of the presence of low vegetation. Over the dense coniferous forest, strong backscatter was observed while higher radiances in both the forward and aftward sensor view zenith directions was measured over the mixed forest. Snow that was known to be beneath the coniferous forest canopy was not detected in our data.