Seasonal snow cover variations in the Nam Co basin of Tibetan Plateau using MODIS data

Snow cover dynamics and snow melt are important hydrological process and water resource for some drainage basins. The variations of seasonal snow cover in the Nam Co basin of Tibetan Plateau from 2000 to 2010 are examined using MODIS data. A method of two thresholds of maximum cloud percentage (10%) and composite days (8) are used to remove cloud cover from MODIS daily snow cover products. Results show that multi-day composite product has annual mean cloud cover of 5.39%, which is much less than annual mean of 43.87%, 51.32%, and 36.79% from daily MODIS/Terra, MODIS/Aqua, and daily MODIS Terra-Aqua combined snow cover products, respectively. The annual mean snow cover from the multi-day composite snow cover product is 12.85%, with largest variations in autumn, followed by winter, with the smallest variation in summer. An overall decrease tendency of snow cover in both spring and summer suggests increased snow melt in the basin, which is consistent with the lake level increase in recent decades. The increased melt of perennial snow cover or glaciers in the summer season could have been due to increased temperature in recent decades.