A method for retrieving soil moisture (SM) profiles using multifrequency, ground-reflected electromagnetic (EM) waves is proposed. In a previous publication, a retrieval technique was developed, which used variations in the angular dependence of the reflectivity to infer the SM profile. In this follow-on work a more practical approach based on the frequency dependence of the modulus of the reflection coefficient for a single incidence angle is extended and its feasibility demonstrated. Two possible approaches are considered: the direct retrieval of the SM profile and the retrieval of the dielectric constant (DC) profile. The former immediately yields the parameter of interest, however, it requires a soil dielectric model linking the DC of the soil to its water content. Such a model, which depends on the type of soil, may not be immediately available. The latter does not require a linking model, but by comparing measured profiles of the DC under dry and wet conditions, the SM profile can be estimated. Both approaches are considered in this article and their feasibility investigated with the help of numerical simulations in the presence of multiplicative noise in the data. For the case of a direct retrieval of the SM profile, a representative soil dielectric model was used. The retrieval procedure was simplified and made more robust and the frequency independence assumption of the DC in the earlier work was removed.

中文翻译：

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利用多频电磁信号反射的土壤水分剖面反演

提出了一种使用多频地面反射电磁 (EM) 波检索土壤水分 (SM) 剖面的方法。在以前的出版物中，开发了一种检索技术，该技术使用反射率的角度依赖性的变化来推断 SM 轮廓。在这项后续工作中，扩展了一种更实用的方法，该方法基于单个入射角的反射系数模数的频率依赖性，并证明了其可行性。考虑了两种可能的方法：直接检索 SM 曲线和检索介电常数 (DC) 曲线。前者立即产生感兴趣的参数，但是，它需要一个土壤介电模型，将土壤的 DC 与其含水量联系起来。这样的模型，取决于土壤的类型，可能不会立即可用。后者不需要链接模型，但通过比较在干燥和潮湿条件下测量的 DC 曲线，可以估计 SM 曲线。本文考虑了这两种方法，并在数据中存在乘性噪声的情况下借助数值模拟研究了它们的可行性。对于直接检索 SM 剖面的情况，使用了具有代表性的土壤介电模型。检索过程被简化并变得更加健壮，并且删除了早期工作中 DC 的频率独立假设。本文考虑了这两种方法，并在数据中存在乘性噪声的情况下借助数值模拟研究了它们的可行性。对于直接检索 SM 剖面的情况，使用了具有代表性的土壤介电模型。检索过程被简化并变得更加健壮，并且删除了早期工作中 DC 的频率独立假设。本文考虑了这两种方法，并在数据中存在乘性噪声的情况下借助数值模拟研究了它们的可行性。对于直接检索 SM 剖面的情况，使用了具有代表性的土壤介电模型。检索过程被简化并变得更加健壮，并且删除了早期工作中 DC 的频率独立假设。