Reflectance and radiance observations obtained with the Moderate Resolution Imaging Spectroradiometer (MODIS) at its bands 4 ( 0.55µm) and 6 (1.6µm) can be used to calculate the Normalized Difference Snow Index (NDSI) which is a measure of the snow cover at the surface.
This NDSI can be used together with a regression to obtain the fractional snow cover (FSC). The data offered here belong to MODIS Collection 006. For this newest release of the MODIS snow cover data set the regression is not applied (unlike done in Collection 005) for reasons detailed in the Users Guide. Users are invited to compute the FSC on their own by taking the regression from the ATBD.
Influence of vegetation, sensor viewing angle, solar illumination, and clouds are taken into account. Collection 006 snow cover data benefit from a number of revisions to both input data and algorithm design as described in the Users Guide. More details can be found in the documents listed in the references listed below.
Last data set update at ICDC: December 6, 2019