Modeling the Scattering of Light by Homogeneous Vegetation in Optical Remote Sensing

Abstract

This paper discusses the problem of radiation transfer in geophysical media, in particular, within homogeneous plant canopies over terrestrial surfaces. The emphasis is placed on the specificities of this problem when it is addressed with the radiation transfer equation classically used in atmospheric sciences. The discussion takes place in the context of remote sensing applications, where the main constraint is to be able to invert the photon transport model against observations to retrieve the properties of the observed media. To facilitate the solution of the radiative coupling between the vegetation and atmospheric layers, the same formal approach is used in both media, and the extinction and differential scattering coefficients are specified in a similar way. The accurate description of the radiation transfer within a vegetation layer is complicated by the fact that both of these coefficients depend on the position of the external sources of radiation, and by the lack of precise knowledge about the radiative boundary conditions at the top and bottom of this layer. Effective solutions to the radiation transfer problem in plant canopies require the introduction of specific hypotheses, for instance, in the treatment of the multiple scattering contribution.