Evaluation of MODIS LAI-FPAR Product Collection 6. Part 2: Validation and IntercomparisonReport as inadecuate




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1

School of Geography, State Key Laboratory of Remote Sensing Science, Beijing Normal University, Beijing 100875, China

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Department of Earth and Environment, Boston University, Boston, MA 02215, USA

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Beijing Key Lab of Spatial Information Integration and Its Applications, Institute of RS and GIS, Peking University, Beijing 100871, China

4

The National Aeronautics and Space Administration NASA Ames Research Center, Moffett Field, CA 94035, USA





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Academic Editors: Alfredo R. Huete and Prasad S. Thenkabail

Abstract The aim of this paper is to assess the latest version of the MODIS LAI-FPAR product MOD15A2H, namely Collection 6 C6. We comprehensively evaluate this product through three approaches: validation with field measurements, intercomparison with other LAI-FPAR products and comparison with climate variables. Comparisons between ground measurements and C6, as well as C5 LAI-FPAR indicate: 1 MODIS LAI is closer to true LAI than effective LAI; 2 the C6 product is considerably better than C5 with RMSE decreasing from 0.80 down to 0.66; 3 both C5 and C6 products overestimate FPAR over sparsely-vegetated areas. Intercomparisons with three existing global LAI-FPAR products GLASS, CYCLOPES and GEOV1 are carried out at site, continental and global scales. MODIS and GLASS CYCLOPES and GEOV1 agree better with each other. This is expected because the surface reflectances, from which these products were derived, were obtained from the same instrument. Considering all biome types, the RMSE of LAI FPAR derived from any two products ranges between 0.36 0.05 and 0.56 0.09. Temporal comparisons over seven sites for the 2001–2004 period indicate that all products properly capture the seasonality in different biomes, except evergreen broadleaf forests, where infrequent observations due to cloud contamination induce unrealistic variations. Thirteen years of C6 LAI, temperature and precipitation time series data are used to assess the degree of correspondence between their variations. The statistically-significant associations between C6 LAI and climate variables indicate that C6 LAI has the potential to provide reliable biophysical information about the land surface when diagnosing climate-driven vegetation responses. View Full-Text

Keywords: Leaf Area Index LAI; Fraction of Photosynthetically-Active Radiation FPAR; MODIS; Collection 6; evaluation; validation; intercomparison Leaf Area Index LAI; Fraction of Photosynthetically-Active Radiation FPAR; MODIS; Collection 6; evaluation; validation; intercomparison





Author: Kai Yan 1,2, Taejin Park 2, Guangjian Yan 1,* , Zhao Liu 2, Bin Yang 2,3, Chi Chen 2, Ramakrishna R. Nemani 4, Yuri Knyazikhin 2 and Ranga B. Myneni 2

Source: http://mdpi.com/



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