TY - JOUR
T1 - Variability in leaf and litter optical properties
T2 - Implications for BRDF model inversions using AVHRR, MODIS, and MISR
AU - Asner, Gregory P.
AU - Wessman, Carol A.
AU - Schimel, David S.
AU - Archer, Steve
N1 - Funding Information:
We sincerely thank Sam Fuhlendorf, Alan Townsend, and Steven Zitzer for assistance in collecting leaf and litter samples. Ann Bateson provided excellent comments and suggestions. G. P. A. especially appreciates the help and warm reception provided by ranchers, cowboys, and friends along the Texas savanna–woodland transect. This work was supported by NASA Innovative Research Grant NAGW-4689, NASA EOS Interdisciplinary Science Award NAGW-2662, and a NASA Earth Systems Science Fellowship Award to G. P. A. The National Center for Atmospheric Research is sponsored by the National Science Foundation.
PY - 1998/3
Y1 - 1998/3
N2 - Canopy radiative transfer models simulate the bidirectional reflectance distribution function (BRDF) of vegetation covers with differing leaf and soil spectral and canopy structural characteristics. Numerical inversion of these models has provided estimates of vegetation structural and biophysical characteristics from multiangle, remotely sensed optical data. The number of angularly unique observations compared to BRDF model parameters largely determines the accuracy of retrievals. To increase this ratio, additional observations of a target must be acquired and the BRDF models and inversions must be simplified. The former will occur when the EOS instruments become available. Previous studies suggest that simplification of BRDF model inversions may best be accomplished by constraining the leaf optical parameters. This study focused on full-range (400-2500 nm) leaf and litter spectral properties convolved to AVHRR, MODIS, and MISR optical channels. Using a diverse array of woody plant and grass species, we found robust and readily usable interrelationships among spectra through correlation, regression, and principal components analyses. Significant differences between green leaf and litter optical properties and their sensor-specific interrelationships indicate that green leaf optical constraints may be useful with BRDF retrievals to detect the onset of canopy senescence. These findings will provide increased efficiency in canopy BRDF model inversions by decreasing the number of observations required to retrieve canopy structural and biophysical information from multiangle remotely sensed data.
AB - Canopy radiative transfer models simulate the bidirectional reflectance distribution function (BRDF) of vegetation covers with differing leaf and soil spectral and canopy structural characteristics. Numerical inversion of these models has provided estimates of vegetation structural and biophysical characteristics from multiangle, remotely sensed optical data. The number of angularly unique observations compared to BRDF model parameters largely determines the accuracy of retrievals. To increase this ratio, additional observations of a target must be acquired and the BRDF models and inversions must be simplified. The former will occur when the EOS instruments become available. Previous studies suggest that simplification of BRDF model inversions may best be accomplished by constraining the leaf optical parameters. This study focused on full-range (400-2500 nm) leaf and litter spectral properties convolved to AVHRR, MODIS, and MISR optical channels. Using a diverse array of woody plant and grass species, we found robust and readily usable interrelationships among spectra through correlation, regression, and principal components analyses. Significant differences between green leaf and litter optical properties and their sensor-specific interrelationships indicate that green leaf optical constraints may be useful with BRDF retrievals to detect the onset of canopy senescence. These findings will provide increased efficiency in canopy BRDF model inversions by decreasing the number of observations required to retrieve canopy structural and biophysical information from multiangle remotely sensed data.
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U2 - 10.1016/S0034-4257(97)00138-7
DO - 10.1016/S0034-4257(97)00138-7
M3 - Article
AN - SCOPUS:0032010666
SN - 0034-4257
VL - 63
SP - 243
EP - 257
JO - Remote Sensing of Environment
JF - Remote Sensing of Environment
IS - 3
ER -