A coherent scattering model for forest canopies based on Monte Carlo simulation of fractal generated trees

A coherent scattering model for tree canopies based on a Monte Carlo simulation of fractal generated trees is investigated in this study. In contrast to the incoherent models based on the radiative transfer theory, the present model is capable of preserving the relative phase of individual scatterer which give rise to the coherent effects and predicting the absolute phase of the backscattered field or equivalently the scattering phase center. In the procedure for Monte Carlo simulation, first tandem generation of tree architectures is implemented by employing the Lindenmayer systems (L-systems), a convenient tool for creating fractal patterns of botanical structures. Since the generating code of tree structures is faithful in preserving the fine features of the simulated tree types, this study provides an efficient approach to examine the effects of tree structures on the radar backscatter. After generating a tree structure, the electromagnetic scattering problem is then treated by considering the tree structure as a cluster of scatterers comprised of cylinders (trunks and branches) and disks (leaves) with specified position, orientation, and size. The scattering solution is obtained by invoking the single scattering theory for a uniform plane wave illumination. In this solution scattering from individual tree components when illuminated by the mean field is computed and then added coherently. The mean field at a given point within the tree structure include the attenuation and phase change due to the scattering and absorption losses of vegetation particles. Finally, the backscattering coefficients are simulated at different frequencies based on the results of the Monte Carlo simulations obtained from a large number of independent trees