A semidiscrete model for the scattering of light by vegetation

An advanced bidirectional reflectance factor model is developed to account for the architectural effects exhibited by homogeneous vegetation canopies for the first orders of light scattering. The characterization of the canopy allows the simulation of the relevant scattering processes as a function of the number, size, and orientation of the leaves, as well as the total height of the canopy. A turbid medium approach is used to represent the contribution to the total reflectance due to the light scattering at orders higher than 1. This model therefore incorporates two previously separate approaches to the problem of describing light scattering in plant canopies and enhances existing models relying on parameterized formulae to account for the hot spot effect in the extinction coefficient. Simulation results using this model compare quite favorably with those produced with a Monte Carlo ray-tracing model for a variety of vegetation cases, The semidiscrete model is also inverted against a well-documented data set of bidirectional reflectance factors taken over a soybean canopy, It is shown that the inversion of the model against a small subset of these measurements leads to reasonable values for the retrieved canopy parameters, These values are used in a direct mode to simulate the bidirectional reflectance factors for solar and viewing conditions significantly different from those available in the subset of soybean data and compared with the full set of actual measurements.