Validation of MODIS FAPAR products in Hulunber grassland of China

Fraction of absorbed photosynthetically active radiation (FAPAR) is one of key variables required in modeling primary production and global climate. FAPAR can be derived from satellite images, for example the MODIS FAPAR. However, validation of the product is a prerequisite for using it to estimate local net primary production (NPP). For this purpose, we carried out in situ measurements of FAPAR in two 2km×2km areas within the temperate meadow-steppe grassland in Hulunber during growing season in 2008. 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. More fieldwork for various types of the grasslands is necessary.