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

Alessandro Cescatti, Barbara Marcolla, Suresh K. Santhana Vannan, Jerry Yun Pan, Miguel O. Román, Xiaoyuan Yang, Philippe Ciais, Robert B. Cook, Beverly E. Law, Giorgio Matteucci, Mirco Migliavacca, Eddy Moors, Andrew D. Richardson, Günther Seufert, Crystal B. Schaaf

Research output: Contribution to journalArticlepeer-review

228 Scopus citations

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 (r 2=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.

Original languageEnglish (US)
Pages (from-to)323-334
Number of pages12
JournalRemote Sensing of Environment
Volume121
DOIs
StatePublished - Jun 2012
Externally publishedYes

Keywords

  • FLUXNET
  • MODIS
  • Plant functional types
  • Remote sensing
  • Surface albedo
  • Terrestrial ecosystems
  • Validation

ASJC Scopus subject areas

  • Soil Science
  • Geology
  • Computers in Earth Sciences

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