
Accession Number : ADP006118
Title : A Scattering Model for Forested Area,
Corporate Author : TEXAS UNIV AT ARLINGTON WAVE SCATTERING RESEARCH CENTER
Personal Author(s) : Karam, M. A. ; Fung, A. K.
Report Date : MAY 1987
Pagination or Media Count : 9
Abstract : A forested area is modeled as a volume of randomly oriented and distributed discshaped, or needleshaped leaves shading a distribution of branches modeled as randomly oriented finitelength, dielectric cylinders above an irregular soil surface. Since the radii of branches have a wide range of sizes, the model only requires the length of a branch to be large compared with its radius of a needleshaped leaf is much smaller than the electromagnetic wavelength. The scattering phase matrices for disc, needle and cylinder are developed in terms of the scattering amplitudes of the corresponding fields which are computed by the Helmholtz integral formula. The extinction coefficients are computed by the Forward scattering theorem. These quantities along with the Kirchoff scattering model for randomly rough surface are used int he standard radiative transfer formulation to compute the backscattering coefficient. Numerical illustrations for the backscattering coefficient are given as a function of the shading factor, incidence angle, leaf orientation distribution, branch orientation distribution and the number density of leaves. Also illustrated are the properties of the extinction coefficient as a function of leaf and branch orientation distributions. Comparisons are made with measured backscattering coefficients from forested areas reported in the literature.
Descriptors : *ELECTROMAGNETIC SCATTERING, *FORESTS, TREES, FORWARD SCATTERING, BACKSCATTERING, MATHEMATICAL MODELS, DIELECTRICS, SHAPE, EXTINCTION, RADIATIVE TRANSFER, NUMERICAL ANALYSIS, SYMPOSIA.
Subject Categories : Radiofrequency Wave Propagation
Electricity and Magnetism
Distribution Statement : APPROVED FOR PUBLIC RELEASE