格陵兰地区GLASS反照率产品质量评价及反照率变化趋势分析

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

    摘要
  • 摘要: 冰雪反照率是影响和评估全球气候变化的重要因子。北极格陵兰岛拥有世界第二大冰盖，定量获取该地区反照率是研究北半球能量收支变化的关键。全球陆表卫星(global land surface satellite，GLASS) 产品系统生产的反照率产品是目前国际上时间序列最长（1981—2017年）的全球反照率产品。利用格陵兰气候观测网络(Greenland climate network, GC-Net)与格陵兰冰架监测计划(programme for monitoring of the Greenland ice sheet, PROMICE)网络观测的反照率数据，评估了格陵兰地区GLASS地表反照率产品的精度；并基于2000—2017年的GLASS地表反照率产品，分析了格陵兰地区7月份反照率的年际变化趋势与空间分布特征。结果表明：GLASS与GC-Net反照率的均方根误差(root mean squared error, RMSE)为0.077 8(决定系数R2=0.490 7)，与PROMICE反照率差异的RMSE为0.078 6(R2=0.899 9)，GLASS产品的反照率数值呈现一定的低估现象，但已满足格陵兰地区冰雪反照率研究的需要。基于2000—2017年7月份格陵兰地区的GLASS反照率变化分析可以看出，格陵兰地区的反照率在此期间整体呈现变小的趋势，平均速率约为0.000 6 /a，变小的地区约占格陵兰总面积的64%；其中，位于格陵兰西部海拔750~1 500 m之间的区域对气候变化最为敏感，反照率变小速率也最大，达到了0.026 /a。

     

    Abstract:
      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.

     

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