Hybrid geometrical-optical radiative-transfer model for the directional reflectance of discontinuous vegetation canopies

Xiaowen Li; Alan H. Strahler; Curtis E. Woodcock

doi:10.1117/12.200742

31 January 1995 Hybrid geometrical-optical radiative-transfer model for the directional reflectance of discontinuous vegetation canopies

Xiaowen Li, Alan H. Strahler, Curtis E. Woodcock

Author Affiliations +

Proceedings Volume 2314, Multispectral and Microwave Sensing of Forestry, Hydrology, and Natural Resources; (1995) https://doi.org/10.1117/12.200742
Event: Satellite Remote Sensing, 1994, Rome, Italy

Abstract

A new model for the bidirectional reflectance of a vegetation cover combines principles of geometric optics and radiative transfer. It relies on gap probabilities and path length distributions to model the penetration of irradiance from a parallel source and the single and multiple scattering of that irradiance in the direction of an observer. The model applies to vegetation covers of discrete plant crowns that are randomly centered both on the plane and within a layer of variable thickness above it. Crowns assume a spheroidal shape with arbitrary height to width ratio. Geometric optics easily models the irradiance that penetrates the vegetation cover directly, is scattered by the soil, and exits without further scattering by the vegetation. Within a plant crown, the probability of scattering is a negative exponential function of path length. Within-crown scattering provides the source for singly-scattered radiation, which exits with probabilities proportional to further path-length distributions in the direction of exitance (including the hotspot effect). Single scattering provides the source for double scattering, and then higher order pairs of scattering are solved successively by a convolution function. As an early exercise in validation, the model is applied to an open jack pine canopy and ground-level irradiance is predicted with good accuracy.

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Xiaowen Li, Alan H. Strahler, and Curtis E. Woodcock "Hybrid geometrical-optical radiative-transfer model for the directional reflectance of discontinuous vegetation canopies", Proc. SPIE 2314, Multispectral and Microwave Sensing of Forestry, Hydrology, and Natural Resources, (31 January 1995); https://doi.org/10.1117/12.200742

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