Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100101, China.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
Sensors (Basel). 2021 Nov 21;21(22):7748. doi: 10.3390/s21227748.
A microwave scattering model is a powerful tool for determining relationships between vegetation parameters and backscattering characteristics. The crown shape of the vegetation canopy is an important parameter in forestry and affects the microwave scattering modeling results. However, there are few numerical models or methods to describe the relationships between crown shapes and backscattering features. Using the Modified Tor Vergata Model (MTVM), a microwave scattering model based on the Matrix Doubling Algorithm (MDA), we quantitatively characterized the effects of crown shape on the microwave backscattering coefficients of the vegetation canopy. FEKO was also used as a computational electromagnetic method to make a complement and comparison with MTVM. In a preliminary experiment, the backscattering coefficients of two ideal vegetation canopies with four representative crown shapes (cylinder, cone, inverted cone and ellipsoid) were simulated: MTVM simulations were performed for the L (1.2 GHz), C (5.3 GHz) and X (9.6 GHz) bands in fully polarimetric mode, and FEKO simulations were carried out for the C (5.3 GHz) band at VV and VH polarization. The simulation results show that, for specific input parameters, the mean relative differences in backscattering coefficients due to variations in crown shape are as high as 127%, which demonstrates that the crown shape has a non-negligible influence on microwave backscattering coefficients of the vegetation canopy. In turn, this also suggests that investigation on effects of plant crown shape on microwave backscattering coefficients may have the potential to improve the accuracy of vegetation microwave scattering models, especially in canopies where volume scattering is the predominant mechanism.
一种微波散射模型是确定植被参数与后向散射特征之间关系的有力工具。植被冠层的冠形是林业中的一个重要参数，影响微波散射建模结果。然而，描述冠形与后向散射特征之间关系的数值模型或方法很少。使用基于矩阵倍增算法（MDA）的微波散射模型——修正的 Tor Vergata 模型（MTVM），我们定量地描述了冠形对植被冠层微波后向散射系数的影响。还使用了 FEKO 作为计算电磁方法，与 MTVM 进行补充和比较。在初步实验中，模拟了具有四种代表性冠形（圆柱、圆锥、倒圆锥和椭球）的两个理想植被冠层的后向散射系数：在全极化模式下对 L（1.2GHz）、C（5.3GHz）和 X（9.6GHz）波段进行了 MTVM 模拟，在 VV 和 VH 极化下对 C（5.3GHz）波段进行了 FEKO 模拟。模拟结果表明，对于特定的输入参数，由于冠形变化引起的后向散射系数的平均相对差异高达 127%，这表明冠形对植被冠层的微波后向散射系数有不可忽视的影响。反过来，这也表明研究植物冠形对微波后向散射系数的影响可能有潜力提高植被微波散射模型的准确性，特别是在体积散射是主要机制的冠层中。
