Full-Wave Simulations of Forest at L-Band With Fast Hybrid Multiple Scattering Theory Method and Comparison With GNSS Signals

Full-wave simulations at L-band using the fast hybrid multiple scattering theory method (FHMSTM) have been applied to the Harvard Forest in Massachusetts using the Soil Moisture Active Passive Validation Experiment 2022 (SMAPVEX22) dataset. Due to the limitations of commercial full-wave electromagnetic solvers, the FHMSTM is our choice considering its efficient and fast solutions. During SMAPVEX22, scientists collected a dataset of tree sizes, tree positions (derived from light detection and ranging measurement), and microwave signals utilizing the Global Navigation Satellite System Transmissometry approach. The 3-D geometric forest model provides 300 trees with heights up to 19 m by processing the dataset. We import the forest model into the FHMSTM and analyze microwave propagation at MA401. The FHMSTM analysis shows that the transmissivity ranges from 0.627 to 0.674 for the vertically polarized incident wave source and from 0.593 to 0.665 for the horizontally polarized incident wave source. To validate the FHMSTM, a comparison is made with the GNSS signals. The comparison results of microwaves are in good agreement, demonstrating the physical results such as shadowing effects under the trees and higher electric amplitudes at some points in forests compared to that of the open area. We also analyze the effects of tapered trees in this study.