Reflectance of snow measured in situ and from space in sub-Arctic areas in Canada and Alaska

Visible and near-infrared measurements of clean snow and dirty snow (both actively melting) were acquired near Yellowknife, NWT, Canada, and over snow-covered glaciers in Alaska. The in situ reflectance at nadir of the dirty snow was approximately 30% lower in the visible part of the spectrum than that of the cleaner snow near Yellowknife. The reflectance curves for the dirty snow are flatter than the curves for the clean snow. The shape of the reflectance curves of actively melting snow near Yellowknife versus fresh snow measured in Alaska was similar in the visible region of the spectrum, but diverged in the near-infrared region. In Alaska, the off-nadir look angle measurements of snow consistently exceeded 1.0 because of enhanced forward scattering. The shape of the reflectance curves and the anisotropic reflectance properties are found more useful in differentiating snow type and moisture state than are actual reflectances