Quality Evaluation of GLASS Albedo Products and Albedo Variation Trends Analysis in Greenland

  Objectives  The albedo of Greenland, the second largest ice sheet in the world, is the key to study the change of energy budget in the northern Hemisphere.Global land surface satellite products system (GLASS) is the global albedo product with the longest time series (1981—2017) in the world.

  Methods  The accuracy of surface albedo of GLASS in Greenland is evaluated using Greenland climate network (GC-Net) and programme for monitoring of the Greenland ice sheet (PROMICE) ground observation data. Based on the surface albedo product of GLASS from 2000 to 2017, the annual variation trend and spatial distribution characteristics of albedo in Greenland in July are analyzed.

  Results  The results show that the root mean square error (RMSE) between GLASS and GC-Net albedo is 0.077 8 (R²=0.490 7), and that between GLASS and PROMICE albedo is 0.078 6 (R²=0.899 9). The results of GLASS albedo change in Greenland in July from 2000 to 2017 show that the albedo of Greenland was decreasing during this period, with an average rate of about 0.000 6/a, and the decreased area accounts for about 64% of the total area of Greenland. Among them, the area between 750 m and 1 500 m above sea level in western Greenland is the most sensitive to climate change and has the highest rate of albedo reduction, reaching 0.026/a.

  Conclusions  The albedo value of GLASS products is underestimated to some extent but it meets the needs of ice and snow albedo research in Greenland. Also, the albedo of Greenland shows a slow interannual decline in July, especially in the western region.