Study of contaminated and mixed objects snow reflectance in Indian Himalaya using spectroradiometer

To understand the effect of contamination and mixed objects on snow reflectance, field experiments were carried out in Indian Himalaya during the winters of 2004–2005 and 2005–2006. The observations suggest, as the amount of contamination increases, the peak of snow reflectance in the visible region shifts toward the higher wavelength range. For snow and soil cover mix, as the proportion of soil cover increases, reflectance increases in SWIR region. For snow and vegetation mix areas, a red edge can be observed if vegetation cover is more than 25%. A significant change in the reflectance is observed in the visible region for snow thickness below 5 cm. Normalized Difference Snow Index (NDSI) and S3 based snow indexes can map soil and ash contaminated snow. In snow–soil mixing (patchy snow), NDSI underestimates the snow cover area and S3 index overestimates. Both the snow indexes can map the snow under vegetation and mixed snow–soil–vegetation areas. Thin snow cover areas can also be mapped using both the indexes. This study will be helpful in developing new indexes and selection of threshold value for snow cover mapping.