Measurement of the bidirectional reflectance of snow at fine spectral and angular resolutions

This paper presents measurements of the bidirectional reflectance factor (BRF) of snow made at finespectral and angular resolution with the Automated Spectro-Goniometer (ASG) for a range of solar zenith angles(0o = 40-50deg) and snow textures (surface grain size = 80 - 240 /an) on two days. Measurements of the stratigraphyof snow texture and density accompanied each day's suite of measurements. The BRF for fine grain, faceted snowexhibited a local backscattering peak at the view zenith near the solar zenith angle, whereas those for mediumgrain, clustered snow did not have a local backscattering peak. The BRF decreased at all wavelengths for anincrease in measured grain radius from 80 /mi to 240 /mi. However, the decrease in BRF in the visible wavelengthswas strongest at Or = 80deg in the forward direction and strongest for A > 1.8 /mi near Or = 30deg in the backwarddirection. As solar zenith angle decreased from 47deg to 41deg the BRF increased near nadir for A < 1.03 /mi but decreased with coherent angular structure for A > 1.03 /mi.