小麦S波段多层后向散射模型

Multiple Layers Backscatter Model of Wheat for S Band

针对麦穗出现后小麦生长期的微波散射特性,基于矢量辐射传输理论(VRT),建立了小麦S波段多层后向散射模型。模型把小麦冠层划分为麦穗层、麦秆叶层和土壤层,并基于能量守恒的矢量辐射传输理论,对电磁波强度的反射、吸收和传输进行了分析,采用5项后向散射贡献构成冠层总后向散射。模型的解析首先采用先进积分方程模型(AIEM)对土壤粗糙面的后向散射进行模拟,然后利用消光矩阵和相矩阵分别计算散射能量的衰减和散射方向的变化,最后利用Mueller矩阵获得最终的解析解。该文选用2011年川西实验场测量的小麦S波段散射数据对构建的模型进行验证与分析,模型的模拟值与实测值吻合较好。研究结果表明麦穗出现后对小麦冠层后向散射影响较大,建模时有必要单独考虑麦穗的影响。

The paper presents a multiple layers backscatter model of wheat for S-band based on vector radiative transfer （VRT） theory, which focuses on the microwave character of wheat at the growth stage that wheat ears appeared. The scattered, absorbed and transferred electromagnetic intensity is analyzed based on the law of energy conservation of VRT, and the wheat canopy is divided into three layers, the ears layer, the stem and leaf layer and the soil layer. Furthermore, the total backscatter is composed by using five back-scattering contributions. An advanced integral equation model （AIEM） is applied to simulate the soil backscatter. The extinction and phase matrices are used to compute the scattering intensity decayed and transferred. In addition, Mueller matrix is used to obtain the backscatter values. The backscatter of S-band, which was measured at the West Sichuan Experiment Location in 2011, is applied to analyze and verify the model. The results show the simulated values agreed well with the measured data, and the wheat ears should be taken into account in modeling as a separate element for its influence to backscatter.