Title
Radiative transfer based scaling of LAI retrievals from reflectance data of different resolutions Radiative transfer based scaling of LAI retrievals from reflectance data of different resolutions
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
Ann Arbor, Mich. ,
Subject
Economics
Physics
Chemistry
Biology
Engineering sciences. Technology
Source (journal)
Remote sensing of environment. - Ann Arbor, Mich.
Volume/pages
84(2003) :1 , p. 143-159
ISSN
0034-4257
0034-4257
ISI
000179518300010
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The problem of how the scale, or spatial resolution, of reflectance data impacts retrievals of vegetation leaf area index (LAI) is addressed in this article. We define the goal of scaling as the process by which it is established that LAI values derived from coarse resolution sensor data equal the arithmetic average of values derived independently from fine resolution sensor data. The increasing probability of land cover mixtures with decreasing resolution is defined as heterogeneity, which is a key concept in scaling studies. The effect of pixel heterogeneity on spectral reflectances and LAI retrievals is investigated with 1-km Advanced Very High Resolution Radiometer (AVHRR) data aggregated to different coarse spatial resolutions. It is shown that LAI retrieval errors at coarse resolution are inversely related to the proportion of the dominant land cover in such pixel. Further, large errors in LAI retrievals are incurred when forests are minority biomes in non-forest pixels compared to when forest biomes are mixed with one another, and vice versa. A physically based scaling with explicit spatial resolution-dependent radiative transfer formulation is developed. The successful application of this theory to scaling LAI retrievals from AVHRR data of different resolutions is demonstrated. These principles underlie our approach to the production and validation of LAI product from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging Spectroradiometer (MISR) aboard the TERRA platform. (C) 2002 Elsevier Science Inc. All rights reserved.
E-info
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