Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network
Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network
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DOI：
10.1016/j.rse.2012.02.019
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发表时间：
2012-06-01
影响因子：
13.5
通讯作者：
Schaaf, Crystal B.
中科院分区：
文献类型：
--
作者：
Cescatti, Alessandro;Marcolla, Barbara;Schaaf, Crystal B.
地表反照率是地球能量平衡中的一个关键参数，因为它影响地球表面直接吸收的太阳辐射量。它在时间和空间上的可变性可以通过使用遥感产品在全球范围内进行检索。为了评估和改进卫星反演的质量，与地面反照率的现场测量进行仔细的相互比较至关重要。为此，我们将MODIS反照率反演与在53个满足严格的土地覆盖均质条件的FLUXNET站点进行的地表测量进行了比较。卫星年均值与现场实测值之间有很好的一致性(r(2)=0.82)。这种不匹配与地表反照率的空间异质性相关，强调了在比较点到像元数据时土地覆盖同质性的相关性。当考虑不同植物功能类型的MODIS反照率的季节模式时，匹配、。地面观测在所有森林地点都是非常好的。相反，在非森林地点(草原、稀树草原、农田)进行的卫星检索低估了整个季节周期的现场测量结果。在草原和农田地点观察到的不匹配很可能是由于这些景观的极端碎片化，高分辨率场景的地质统计属性证实了这一点。(C)2012 Elsevier Inc.保留所有权利。
Surface albedo is a key parameter in the Earth's energy balance since it affects the amount of solar radiation directly absorbed at the planet surface. Its variability in time and space can be globally retrieved through the use of remote sensing products. To evaluate and improve the quality of satellite retrievals, careful intercomparisons with in situ measurements of surface albedo are crucial. For this purpose we compared MODIS albedo retrievals with surface measurements taken at 53 FLUXNET sites that met strict conditions of land cover homogeneity. A good agreement between mean yearly values of satellite retrievals and in situ measurements was found (r(2) = 0.82). The mismatch is correlated with the spatial heterogeneity of surface albedo, stressing the relevance of land cover homogeneity when comparing point to pixel data. When the seasonal patterns of MODIS albedo are considered for different plant functional types, the match,. with surface observations is extremely good at all forest sites. On the contrary, satellite retrievals at non-forested sites (grasslands, savannas, croplands) underestimate in situ measurements across the seasonal cycle. The mismatch observed at grassland and cropland sites is likely due to the extreme fragmentation of these landscapes, as confirmed by geostatistical attributes derived from high resolution scenes. (c) 2012 Elsevier Inc. All rights reserved.