MODIS/FAPAR在呼伦贝尔草原区的精度验证与分析

验证MODIS/FAPAR产品在温性草原地区的精度，以提高NPP估算精度，为区域碳平衡监测及合理安排草地畜牧业生产提供服务。该文选取两块2 km×2 km温性草甸类草地设计和进行FAPAR实测试验。以分辨率为32 m的北 京-1号卫星遥感数据对样地进行异质性分析，然后进行尺度上推，利用地面实测数据对1km的MODIS/FAPAR草原地区产品进行验证。结果表明，在草地生长季，MODIS/FAPAR产品的草地FAPAR季节变化与实测FAPAR季节变化趋势基本一致，但总体要比实测FAPAR要高，针茅样地MODIS/FAPAR值比实测值要高约13.7%，羊草样地为18.7%。MODIS/FAPAR算法对于局部区域过于粗糙，对草地类型多样的中国来说，需更多的野外试验资料，以反演适合不同草地类型的FAPAR算法。

Validation of MODIS FAPAR in the Hulunber grassland of China

The accuracy validation of the MODIS/FAPAR product is a prerequisite for using it to estimate local net primary production (NPP), and to supply service for monitoring the balance of region carbon and arranging production of grassland animal husbandry rationally. For this purpose, we designed and carried out in-situ measurements of FAPAR in two 2 km×2 km areas within the temperate meadow-steppe grassland in Hulunber during growing season in 2008, and analyzed heterogeneity of the two sites using image of Beijing-1 satellite with resolution of 32 m, and then scaled up and validated MODIS/FAPAR products with in-situ measured data in grassland area. The results showed that the MODIS FAPAR product reflected very well the seasonal dynamics of in-situ FAPAR, but tended to overestimate the value with averaged relative error of 13.7% in the Stipa Baicalensis site and 18.7% in the Leymus Chinensis site. The MODIS/FAPAR algorithm was derived based on the global land cover map, which may be too broad for local areas. More fieldworks for various types of the grasslands are necessary.