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The Impact of Soil Reflectance on the Quantification of the Green Vegetation Fraction from NDVIThe green vegetation fraction (Fg) is an important climate and hydrologic model parameter. A common method to calculate Fg is to create a simple linear mixing rnodeP between two NDVI endmembers: bare soil NDVI (NDVI(sub o)) and full vegetation NDVI (NDVI(sub infinity)). Usually it is assumed that NDVI(sub o), is close to zero (NDVI(sub o) approx.-0.05) and is generally chosen from the lowest observed NDVI values. However, the mean soil NDVI computed from 2906 samples is much larger (NDVI=0.2) and is highly variable (standard deviation=O. 1). We show that the underestimation of NDVI(sub o) yields overestimations of Fg. The largest errors occur in grassland and shrubland areas. Using parameters for NDVI(sub o) and NDVI(sub infinity) derived from global scenes yields overestimations of Fg ((Delta) Fg*) that are larger than 0.2 for the majority of U.S. land cover types when pixel NDVI values are 0.2
Document ID
Document Type
Reprint (Version printed in journal)
Montandon, L. M. (Colorado Univ. Boulder, CO, United States)
Small, E. E. (Colorado Univ. Boulder, CO, United States)
Date Acquired
August 24, 2013
Publication Date
April 15, 2008
Publication Information
Publication: Remote Sensing of Environment: Remote Sensing Data Assimilation Special Issue
Volume: 112
Issue: 4
Subject Category
Earth Resources and Remote Sensing
Distribution Limits