An analytic radiative transfer model for a coupled atmosphere and leaf canopy

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Abstract
A new analytical radiative transfer model of a leaf canopy is developed that approximates multiple‐scattering radiance by a four‐stream formulation. The canopy model is coupled to a homogeneous atmospheric model as well as a non‐Lambertian lower boundary soil surface. The same four‐stream formulation is also used for the calculation of multiple scattering in the atmosphere. Comparisons of radiance derived from the four‐stream model with those calculated by an iterative numerical solution of the radiative transfer equation show that the analytic model has a very high accuracy, even with a turbid atmosphere and a very dense canopy in which multiple scattering dominates. Because the coupling of canopy and atmospheric models fully accommodates anisotropic surface reflectance and atmospheric scattering and its effect on directional radiance, the model is especially useful for application to directional radiance and measurements obtained by remote sensing. Retrieval of biophysical parameters using this model is under investigation.