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Remote Sens. 2016, 8(4), 275; doi:10.3390/rs8040275

A New Global fAPAR and LAI Dataset Derived from Optimal Albedo Estimates: Comparison with MODIS Products

1
Department of Geography, University College London, Gower Street, London WC1E 6BT, UK
2
NERC National Center for Earth Observation (NCEO), Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
3
Imaging Group, Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St Mary, London RH5 6NT, UK
4
The Inversion Lab, Martinistr. 21, Hamburg 20251, Germany
5
EC Commission, Joint Research Center, Institute for Environment and Sustainability Joint Research Center, Via E. Fermi 2749, Ispra (VA) 21027, Italy
*
Author to whom correspondence should be addressed.
Academic Editors: Dongdong Wang and Prasad S. Thenkabail
Received: 8 January 2016 / Revised: 3 March 2016 / Accepted: 16 March 2016 / Published: 25 March 2016

Abstract

We present the first comparison between new fAPAR and LAI products derived from the GlobAlbedo dataset and the widely-used MODIS fAPAR and LAI products. The GlobAlbedo-derived products are produced using a 1D two-stream radiative transfer (RT) scheme designed explicitly for global parameter retrieval from albedo, with consistency between RT model assumptions and observations, as well as with typical large-scale land surface model RT schemes. The approach does not require biome-specific structural assumptions (e.g., cover, clumping, understory), unlike more detailed 3D RT model approaches. GlobAlbedo-derived values of fAPAR and LAI are compared with MODIS values over 2002–2011 at multiple flux tower sites within selected biomes, over 1200 × 1200 km regions and globally. GlobAlbedo-derived fAPAR and LAI values are temporally more stable than the MODIS values due to the smoothness of the underlying albedo, derived via optimal estimation (assimilation) using an a priori estimate of albedo derived from an albedo “climatology” (composited multi-year albedo observations). Parameters agree closely in timing but with GlobAlbedo values consistently lower than MODIS, particularly for LAI. Larger differences occur in winter (when values are lower) and in the Southern hemisphere. Globally, we find that: GlobAlbedo-derived fAPAR is ~0.9–1.01 × MODIS fAPAR with an intercept of ~0.03; GlobAlbedo-derived LAI is ~0.6 × MODIS LAI with an intercept of ~0.2. Differences arise due to the RT model assumptions underlying the products, meaning care is required in interpreting either set of values, particularly when comparing to fine-scale ground-based estimates. We present global transformations between GlobAlbedo-derived and MODIS products. View Full-Text
Keywords: fAPAR; LAI; albedo; radiative transfer; vegetation; MODIS; GlobAlbedo fAPAR; LAI; albedo; radiative transfer; vegetation; MODIS; GlobAlbedo
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Disney, M.; Muller, J.-P.; Kharbouche, S.; Kaminski, T.; Voßbeck, M.; Lewis, P.; Pinty, B. A New Global fAPAR and LAI Dataset Derived from Optimal Albedo Estimates: Comparison with MODIS Products. Remote Sens. 2016, 8, 275.

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