Atmospheric effects in the remote sensing of surface albedo and radiation absorption by vegetation canopies

Abstract

A one‐dimensional turbid medium model of a vegetation canopy that includes specular reflection and the hot spot effect is used to calculate surface bidirectional reflectance factors (BRFs), albedo, absorbed solar and photosynthetically active radiation and, canopy photosynthetic efficiency. Simulated surface BRF distribution is then used as the lower boundary condition in the atmospheric radiative transfer problem. A horizontally homogeneous cloudless midlatitude continental atmosphere with both molecular and aerosol loading is assumed throughout. The dynamics of surface and planetary albedo are examined for varying surface and atmospheric parameters. The relationship between planetary and surface albedo and its sensitivity to problem parameters is investigated. An algorithm for the estimation of surface albedo is outlined and the magnitude of errors incurred is discussed. An effort is made to relate canopy radiation absorption to top‐of‐the‐atmosphere spectral vegetation indices and the sensitivity of these relationships to problem parameters is evaluated.