The Diffuse Reflection Radiation from the Atmosphere Bounded by the Hybrid Surface of a Diffuse and Specular Reflector

Abstract

The intensity and the degree of polarization of the radiation diffusely reflected by an inhomogeneous atmosphere are computed by using the adding method (Takashima et al., 1975), where the atmosphere is composed of twelve homogeneous composite layers. The atmosphere-ground system used for the numerical computations is such a realistic model that the effect of scattering due to aerosols distribution with height and the absorption effect by ozone are taken into account. In addition, the atmosphere is bounded by a hybrid surface of a diffuse and specular reflector. In this paper, computations are selected in the wavelength region of 0.65μm which is applicable for the study of VHRR and VISSR data (0.6-1.0μm). Elterman's values (1968) are adopted for the optical thicknesses of aerosol, Rayleigh and ozone constituents. Deirmendjian model L (1969) is used for the aerosol size distribution with a real index of refraction of 1.34. Computational results show that (1) at a low sun elevation, a high intensity value is noted in the forward direction. This is more pronounced in the case of a specular surface than that of the Lambert surface. (2) At a high sun elevation, an intensity peak exists in the specular direction if the surface is a hybrid mode. (3) For a hybrid surface, the lower the sun elevation, the higher the albedo of the atmosphere-ground system will be. (4) The degree of polarization decreases rapidly with the increase of the Lambert component of reflection. These results reflect the application for parameterizing surface characteristics in terms of the diffuse reflection radiation and hence for monitoring the surface by remote sensing satellite measurements.