**2. Datasets**

Three types of datasets were used to quantitatively determine the spatial representativeness of the MODIS daily albedo product: (1) Tower-measured surface albedo datasets from AmeriFlux sites were used as field truth to calibrate 30 m albedo data. (2) The MODIS daily albedo product MOD43A3 (V006, 500 m, daily) was assessed, and annual land cover data were downloaded to identify different land cover types. (3) Landsat TM level-one data were used to estimate the 30 m spatial resolution of the albedo, which was then used as the spatial complete high resolution data to evaluate the spatial representativeness of the MODIS 500 m spatial resolution albedo product.

### *2.1. AmeriFlux Site Data*

The AmeriFlux network is a community of sites and scientists measuring the amounts of carbon, water, energy fluxes, and related environmental variables in ecosystems across the Americas [46]. It supplies a long period of field observations and features wide coverage of forests, grasslands, croplands, shrub lands, wetlands, savannas, and other geographies (e.g., urban). A total of 166 sites are distributed in North and South America, of which 109 feature continuous radiation measurement. Level-2 data of downward and upward radiation from these 109 sites were downloaded from the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL). The instruments mounted on the tower including Kipp and Zonen (CNR1, CM-3, OR CM-6), and the Eppley-PSP albedometer/pyranometer. The instruments were fitted with domes to collect radiation fluxes in the broadband shortwave domain (0.3–2.8 μm). Data received from each site were reviewed and incorporated into the network of the AmeriFlux database. The data review process includes checking for consistent units, naming conventions, reporting intervals, and reforming to ensure consistency with the larger network-wide database [47]. Radiation data were collected every half hour during the years indicated in Table 1 for each site. The overall range of years recorded at one site or more is 1995 to 2013. A region of 10 × 10 km around each site was selected as the research area. Information pertaining to the sites used in this study—site name, latitude, longitude, land cover type, and the years when data are available—is listed in Table 1.


**Table 1.** Flux sites used in the analysis.



**Table 1.** *Cont*.
