Abstract
The objective of this paper is to present the contribution of a new dielectric constant characterisation for the modelling of radar backscattering behaviour. Our analysis is based on a large number of radar measurements acquired during different experimental campaigns (Orgeval'94, Pays de Caux'98, 99). We propose a dielectric constant model, based on the combination of contributions from both soil and air fractions. This modelling clearly reveals the joint influence of the air and soil phases, in backscattering measurements over rough surfaces with large clods. A relationship is established between the soil fraction and soil roughness, using the Integral Equation Model (IEM), fitted to real radar data. Finally, the influence of the air fraction on the linear relationship between moisture and the backscattered radar signal is discussed.
Highlights
Soil moisture and roughness parameters play a key role in hydrological and climate studies.Considerable effort has been devoted to the study of radar backscattering responses from natural surfaces, in active microwave remote sensing [1,2,3,4,5]
In this paper we deal with a scientific question, often neglected in our previous studies, related to the computation of the dielectric constant used in backscattering models for the estimation of soil roughness or moisture
For medium or rough surfaces, we have observed the presence of a significant air fraction that could be present between clods, or below clods
Summary
Soil moisture and roughness parameters play a key role in hydrological and climate studies. A linear relationship between surface moisture and backscattered radar signals has been proposed [1] This approach was validated by a large number of experimental studies [15, 16]. For agricultural soils with rough surfaces, we observe clods with a large air fraction between them This air fraction is not taken into account when estimating the dielectric constant. We propose a new modelling process for the dielectric constant, in order to include the effects of the air fraction. It presents an analysis of the relationship between soil fraction and radar signal behaviour, and its influence on the relationship between radar signal and soil moisture.
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