A three-dimensional radiative transfer method for optical remote sensing of vegetated land surfaces

Abstract

In the application of remote sensing at optical wavelengths to vegetated land surfaces from satellite-borne high-resolution instruments, such as those scheduled for the Earth Observing System, an understanding of the various physical mechanisms that contribute to the measured signal is important. In this context, numerical radiative transfer in three-dimensional coupled medium of atmosphere and vegetation has several applications, as in the development of correction routines for atmospheric perturbations, target information retrieval techniques, study of terrain elevation and adjacency effects, etc. A numerical method for solving the radiative transfer equation in three spatial dimensions was recently developed and analyzed for its numerical behavior. In this article, continued development of the method is reported, including an efficient acceleration algorithm. The reliability of coding and accuracy of the algorithm are evaluated by benchmarking. Parameterization of the method and results of a simulation are presented to document the utility of the code for applications in optical remote sensing studies of vegetated land surfaces. A simple model of the hot spot effect and sample calculations are presented. Finally, the radiative transfer method is tested with experimental data of vegetation canopy reflectance factors at two wavelengths.