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Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network

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https://ir.library.oregonstate.edu/concern/articles/k3569488n

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Abstract
  • 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 (r² = 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.
  • Keywords: FLUXNET, Remote sensing, Validation, Surface albedo, Plant functional types, MODIS, Terrestrial ecosystems
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  • Cescatti, A., Marcolla, B., Vannan, S., Pan, J., Roman, M., Yang, X., . . . . (2012). Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network. REMOTE SENSING OF ENVIRONMENT, 121, 323-334. doi: 10.1016/j.rse.2012.02.019
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  • 121
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  • We acknowledge the support to data harmonization provided by CarboEuropeIP, FAO-GTOS-TCO, iLEAPS (the Integrated Land Ecosystem-Atmosphere Processes Study, a core project of IGBP), Max Planck Institute for Biogeochemistry, National Science Foundation, University of Tuscia, Université Laval and Environment Canada and US Department of Energy and the database development and technical support from Berkeley Water Center, Lawrence Berkeley National Laboratory, Microsoft Research eScience, Oak Ridge National Laboratory, University of California — Berkeley, and University of Virginia. The processing of MODIS data has been supported by NASA grant NNX08AE94A. Support for C. Schaaf and X. Yang was provided by NASA grant NNX08AE94A.
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