How does snow impact the albedo of vegetated land surfaces as analyzed with MODIS data?

Albedo derived from MODIS observations is found to be very stable during November 2000-January 2001. We analyze shortwave albedo under snow and snow-free conditions by IGBP land cover types. Snow changes the spectral property of the surface reflectivity and causes high heterogeneity in the surface albedo between and within land types. The mean black sky (or direct beam) albedo at local solar noon for snow-covered forests is less than 0.30 in the shortwave (0.3-5.0 μm), but it reaches 0.57 for snow-covered grassland and barren. Although we are unable to further separate within-class albedos with fractional tree cover, we find that the normalized difference snow index (NDSI) is highly correlated with surface albedo and hence can be taken as a measure of snow, soil and canopy fraction.