Validation of MODIS Albedo Products of Paddy Fields in Japan
Validation of MODIS Albedo Products of Paddy Fields in Japan
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DOI：
10.1109/tgrs.2006.882266
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发表时间：
2007
影响因子：
8.2
通讯作者：
J. Susaki;Y. Yasuoka;K. Kajiwara;Y. Honda;K. Hara
中科院分区：
文献类型：
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作者：
J. Susaki;Y. Yasuoka;K. Kajiwara;Y. Honda;K. Hara
在日本千叶进行了一项研究，通过对稻田中短波波段辐射的实地测量来验证中分辨率成像光谱仪（MODIS）的辐射产品。从实地测量的点数据到1公里分辨率的空间尺度差异很大，使验证过程复杂化。为了评估不同空间尺度的这种影响，使用了高级星载热发射和反射辐射计（ASTER）和增强型专题制图仪（ETM+）数据。从3个角度考察了空间尺度对空间变异的影响：1）基于点的空间变异与均匀区域空间变异均值的比较; 2）基于点的空间变异与1 km聚集空间变异的比较; 3）均匀区域空间变异半方差函数的估计。在观点2）的实现中，应用Liang的回归模型将ASTER反射率转换为短波波段反射率。使用点扩散函数估算了1公里ASTER的辐射通量，并以同样的方式估算了1公里ETM+辐射通量。所有的结果表明，测量站点周围的区域可以被假定为是均匀的，表明在大多数时间段的空间分辨率差异的影响可以忽略不计。将基于地面点的反射率与MODIS实际反射率（由MODIS黑天空反射率、白天空反射率和一部分漫射天空反射率估算）进行比较，结果表明，日本稻田的MODIS反射率产品的精度绝对值（均方根误差）在0.026以内，相对值在15.1
A study was conducted in Chiba, Japan, to validate Moderate Resolution Imaging Spectroradiometer (MODIS) albedo products by taking the field measurements of shortwave band albedos in paddy fields. A large difference in spatial scale, from field-measured point data to 1-km resolution, complicates the validation process. To assess such effect of different spatial scales, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper Plus (ETM+) data were used. Spatial scale effects on the albedo were examined from three viewpoints: 1) comparison between point-based albedo and mean of albedo in homogeneous area; 2) comparison between point-based albedo and 1-km aggregated albedo; and 3) assessment of semivariogram of albedo in homogeneous area. In implementation of viewpoint 2), Liang's regression model was applied to convert ASTER reflectance into shortwave band albedo. The 1-km ASTER albedo was estimated using the point spread function, and in the same manner, 1-km ETM+ albedo was estimated. All results represent that an area around the measurement site can be assumed to be homogeneous, indicating negligible effects of spatial resolution difference during most of the periods. Comparison of ground-point-based albedos with MODIS actual albedo, estimated from MODIS black-sky albedo, white-sky albedo, and a fraction of diffuse skylight, showed that the accuracy of MODIS albedo products for paddy fields in Japan is within approximately 0.026 by absolute value (root-mean-square error) and 15.1% by relative value