Hybrid Method for Full-Wave Simulations of Forests at L-Band

The full-wave simulations of 3D Maxwell equations of forests at L-band are carried out with a two-step hybrid method. The tallest trees considered include one 8-meter tall trunk, 18 primary branches and 108 secondary branches. In the first step, the T-matrix of a single tree in the representation of vector cylindrical waves (VCW) is calculated by using the far-field scattering amplitudes obtained from the commercial solver FEKO. In the second step, the wave multiple scattering theory (W-MST) as represented by the Foldy-Lax equations is used to account for the wave interactions among different trees. The accuracy of the hybrid method is validated by showing that the computed solutions of three trees are in good agreement with those solved from FEKO. Next the hybrid method is used for Monte Carlo simulations of forest stands with up to 30 trees. The dependences of the solutions on tree heights and tree densities are illustrated. The results show that the full-wave based transmissivities are much larger than those obtained from the radiative transfer equation (RTE) model.