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The scattering and extinction coefficients of the SAIL canopy reflectance model are derived for the case of a fixed arbitrary leaf inclination angle and a random leaf azimuth distribution. The SAIL model includes the uniform model of G. H. Suits as a special case and its main characteristics are that canopy variables such as leaf area index and the leaf inclination distribution function are used as input parameters and that it provides more realistic angmlar profiles of the directional reflectance as a function of the view angle or the solar zenith angle.

Abstract. This paper presents the model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes), which is a vertical (1-D) integrated radiative transfer and energy balance model. The model links visible to thermal infrared radiance spectra (0.4 to 50 µm) as observed above the canopy to the fluxes of water, heat and carbon dioxide, as a function of vegetation structure, and the vertical profiles of temperature. Output of the model is the spectrum of outgoing radiation in the viewing direction and the turbulent heat fluxes, photosynthesis and chlorophyll fluorescence. A special routine is dedicated to the calculation of photosynthesis rate and chlorophyll fluorescence at the leaf level as a function of net radiation and leaf temperature. The fluorescence contributions from individual leaves are integrated over the canopy layer to calculate top-of-canopy fluorescence. The calculation of radiative transfer and the energy balance is fully integrated, allowing for feedback between leaf temperatures, leaf chlorophyll fluorescence and radiative fluxes. Leaf temperatures are calculated on the basis of energy balance closure. Model simulations were evaluated against observations reported in the literature and against data collected during field campaigns. These evaluations showed that SCOPE is able to reproduce realistic radiance spectra, directional radiance and energy balance fluxes. The model may be applied for the design of algorithms for the retrieval of evapotranspiration from optical and thermal earth observation data, for validation of existing methods to monitor vegetation functioning, to help interpret canopy fluorescence measurements, and to study the relationships between synoptic observations with diurnally integrated quantities. The model has been implemented in Matlab and has a modular design, thus allowing for great flexibility and scalability.

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The differential equations describing radiative transfer in vegetative canopies as given by Suits are generalized and solved to derive a layer scattering matrix. Layer scattering matrices can be applied to the calculation of optical parameters for multilayer ensembles according to the Adding method. The application to atmospheric scattering is demonstrated by explaining path radiance, sky radiance, and other quantities in terms of elements from a layer scattering matrix and a surhce reflectance matrix. By combining scattering matrices originating from atmospheric layers with those from earth objects, earth observation models can be constructed. These may become valuable tools in the study of various remote sensing problems. Introductionwater bodies. This results in mathematical models that predict the intensity of Remote sensing of earth objects in the scattered or reflected radiation for given visible to middle infrared wavelength re-directions of sunlight and view as a funcgion is a powerful technique for providing tion of atmospheric and object parameinformation on earth resources rapidly and ters. In this way the quantitative relationover large areas. In the extraction of in-ships between object parameters and reformation from multispectral digital image motely sensed data can be established for data acquired by remote sensing missions, given conditions of observation. An excelseveral levels of sophistication can be dis-lent review of such models, with special tinguished. Some of these techniques, such emphasis on the applicability to remote as visual interpretation of enhanced color sensing problems, is given in Slater (1980). composite imagery or routines for auto-Of particular interest are the vegetation matic classification, already offer much canopy reflectance model of Suits (1972) valuable information for relatively little and the atmospheric model of Turner effort. In other cases, however, especially (1973), since these models are not too when quantitative data are to be ex-complex, require little computer proctracted, these techniques fall short be-essing power, and yet are reasonably recause the extraction of this type of infor-alistic. mation requires more insight into the The analytical model of Suits is based physical processes involved in the interac-on two extensions of the Kubelka-Munk tion of radiation with objects on earth (1931) theory, which describes the scatand with the atmosphere. These interac-tering and extinction of isotropic diffuse tions can be investigated by the appli-fluxes in upward and downward direccation of radiative transfer theory to prob-tion. The first extension is the addition of lems such as atmospheric scattering and specular sunlight with its associate extincnon-Lambertian reflection characteristics tion and scattering coefficients, which of objects like vegetation canopies and leads to the Dtmtley (1942) equations,