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Calculation of the angular radiance distribution for a coupled atmosphere and canopyThe radiative transfer equations for a coupled atmosphere and canopy are solved numerically by an improved Gauss-Seidel iteration algorithm. The radiation field is decomposed into three components: unscattered sunlight, single scattering, and multiple scattering radiance for which the corresponding equations and boundary conditions are set up and their analytical or iterational solutions are explicitly derived. The classic Gauss-Seidel algorithm has been widely applied in atmospheric research. This is its first application for calculating the multiple scattering radiance of a coupled atmosphere and canopy. This algorithm enables us to obtain the internal radiation field as well as radiances at boundaries. Any form of bidirectional reflectance distribution function (BRDF) as a boundary condition can be easily incorporated into the iteration procedure. The hotspot effect of the canopy is accommodated by means of the modification of the extinction coefficients of upward single scattering radiation and unscattered sunlight using the formulation of Nilson and Kuusk. To reduce the computation for the case of large optical thickness, an improved iteration formula is derived to speed convergence. The upwelling radiances have been evaluated for different atmospheric conditions, leaf area index (LAI), leaf angle distribution (LAD), leaf size and so on. The formulation presented in this paper is also well suited to analyze the relative magnitude of multiple scattering radiance and single scattering radiance in both the visible and near infrared regions.
Document ID
19930060301
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Liang, Shunlin (NASA Headquarters Washington, DC United States)
Strahler, Alan H. (Boston Univ. MA, United States)
Date Acquired
August 16, 2013
Publication Date
March 1, 1993
Publication Information
Publication: IEEE Transactions on Geoscience and Remote Sensing
Volume: 31
Issue: 2
ISSN: 0196-2892
Subject Category
EARTH RESOURCES AND REMOTE SENSING
Funding Number(s)
CONTRACT_GRANT: NAS5-30917
CONTRACT_GRANT: NAS5-31369
CONTRACT_GRANT: NSF INT-90-14263
CONTRACT_GRANT: NAGW-2082
Distribution Limits
Public
Copyright
Other