NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Vegetation canopy PAR absorptance and the normalized difference vegetation index - An assessment using the SAIL modelRelationships are studied between the normalized-difference vegetation index (NDVI) and absorbed photosynthetically active radiation (APAR) in a vegetation canopy. The SAIL model of bidirectional canopy radiative transfer is employed to compare NDVI measurements that are instantaneous with diurnally integrated canopy APAR capacity. The NDVI measurements - taken at solar-zenith angles of more than 60 deg and sensor views of less than 40 deg from nadir - give stable near-linear estimates of diurnal APAR capacity. Discrepancies in the relations between APAR and NDVI are associated with variations in the optical properties of the canopy and with background spectral reflectance. The results are significant for the practical use of these remote sensing techniques but suggest that instantaneous observations can be used to characterize the diurnally integrated APAR in vegetation canopies.
Document ID
19920043715
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Goward, Samuel N.
(NASA Headquarters Washington, DC United States)
Huemmrich, Karl F.
(Maryland, University College Park, United States)
Date Acquired
August 15, 2013
Publication Date
February 1, 1992
Publication Information
Publication: Remote Sensing of Environment
Volume: 39
ISSN: 0034-4257
Subject Category
Earth Resources And Remote Sensing
Accession Number
92A26339
Funding Number(s)
CONTRACT_GRANT: NAGW-1152
CONTRACT_GRANT: NAG5-903
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available