Snow is an important actor in regulating climate. It acts as a blocker for sunlight, cooling down the planet but also plays an important role in hydrological cycle of the Planet, snow and glacier water representing one of the most important water resource in dry seasons for an important population of the world.
The 10 days maximum Snow Cover Extent (10days SCE) was computed using Google Earth Engine (GEE) cloud platform and MOD10A1 Snow Cover Daily Global as a base input. MOD10A1 is based on a snow mapping algorithm that employs Normalized Difference Snow Index (NDSI) and other criteria tests such as data screens applied to alleviate snow detection commission errors and flag uncertain snow detection. (https://modis-snow-ice.gsfc.nasa.gov/uploads/snow_user_guide_C6.1_final_revised_april.pdf)
As a Maximum Value Composite, 10 days SCE takes in account the maximum value per pixel of NDSI on the 10 days interval. The 10 days intervals are defined as 1-10, 11-20 and 21-end of every month. Also additional filtering is applied to reduce uncertainty as follows:
-filtering out low qulity pixels based on internal bit flags
-filtering out pixels with values lower than 30
-accross the summer months (from May through September) to exclude pixels identified as snow due to summer storms (ice in summer storms clouds) , a filter was applied to exclude pixels with less than 2 observations as snow in the same pixel and also filter out snow below 2000 meters (in the Danube basin in the summer months snow below 2000 is not something that will usually happen)