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generating vegetation leaf area index earth system data record from multiple sensorsThe evaluation of a new global monthly leaf area index (LAI) data set for the period July 1981 to December 2006 derived from AVHRR Normalized Difference Vegetation Index (NDVI) data is described. The physically based algorithm is detailed in the first of the two part series. Here, the implementation, production and evaluation of the data set are described. The data set is evaluated both by direct comparisons to ground data and indirectly through inter-comparisons with similar data sets. This indirect validation showed satisfactory agreement with existing LAI products, importantly MODIS, at a range of spatial scales, and significant correlations with key climate variables in areas where temperature and precipitation limit plant growth. The data set successfully reproduced well-documented spatio-temporal trends and inter-annual variations in vegetation activity in the northern latitudes and semi-arid tropics. Comparison with plot scale field measurements over homogeneous vegetation patches indicated a 7% underestimation when all major vegetation types are taken into account. The error in mean values obtained from distributions of AVHRR LAI and high-resolution field LAI maps for different biomes is within 0.5 LAI for six out of the ten selected sites. These validation exercises though limited by the amount of field data, and thus less than comprehensive, indicated satisfactory agreement between the LAI product and field measurements. Overall, the intercomparison with short-term LAI data sets, evaluation of long term trends with known variations in climate variables, and validation with field measurements together build confidence in the utility of this new 26 year LAI record for long term vegetation monitoring and modeling studies.
Document ID
20110005519
Document Type
Reprint (Version printed in journal)
Authors
Ganguly, Sangram
(Boston Univ. Boston, MA, United States)
Samanta, Arindam
(Boston Univ. Boston, MA, United States)
Schull, Mitchell A.
(Boston Univ. Boston, MA, United States)
Shabanov, Nikolay V.
(National Environmental Satellite Service Camp Springs, MD, United States)
Milesi, Cristina
(NASA Ames Research Center Moffett Field, CA, United States)
Nemani, Ramajrushna R,
(NASA Ames Research Center Moffett Field, CA, United States)
Knyazikhin, Yuri
(Boston Univ. Boston, MA, United States)
Myneni, Ranga B.
(Boston Univ. Boston, MA, United States)
Date Acquired
August 25, 2013
Publication Date
July 29, 2008
Publication Information
Publication: Remote Sensing of Environment
Volume: 112
Issue: 12
ISSN: 0034-4257
Subject Category
Earth Resources and Remote Sensing
Funding Number(s)
CONTRACT_GRANT: NNX08AE81G
Distribution Limits
Public
Copyright
Other