Journal ArticleDOI
Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations
TLDR
In this article, the authors evaluate the microwave dielectric behavior of soil-water mixtures as a function of water content, temperature, and soil textural composition, and present two mixing models to account for the observed behavior: 1) a semi-empirical refractive mixing model that accurately describes the data and requires only volumetric moisture and soil texture as inputs, and 2) a theoretical four-component mixing model explicitly accounts for the presence of bound water.Abstract:
This is the first paper in a two-part sequence that evaluates the microwave dielectric behavior of soil-water mixtures as a function of water content, temperature, and soil textural composition. Part I presents the results of dielectric constant measurements conducted for five different soil types at frequencies between 1.4 and 18 GHz. Soil texture is shown to have an effect on dielectric behavior over the entire frequency range and is most pronounced at frequencies below 5 GHz. In addition, the dielectric properties of frozen soils suggest that a fraction of the soil water component remains liquid even at temperatures of -24° C. The dielectric data as measured at room temperature are summarized at each frequency by polynomial expressions dependent upon both the volumetric moisture content m and the percentage of sand and clay contained in the soil; separate polynomial expressions are given for the real and imaginary parts of the dielectric constant. In Part II, two dielectric mixing models will be presented to account for the observed behavior: 1) a semiempirical refractive mixing model that accurately describes the data and requires only volumetric moisture and soil texture as inputs, and 2) a theoretical four-component mixing model that explicitly accounts for the presence of bound water.read more
Citations
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Journal ArticleDOI
An empirical model and an inversion technique for radar scattering from bare soil surfaces
TL;DR: An inversion technique was developed for predicting the rms height of the surface and its moisture content from multipolarized radar observations, which was found to yield very good agreement with the backscattering measurements of the present study.
Journal ArticleDOI
Measuring soil moisture with imaging radars
P. Dubois,J.J. van Zyl,T. Engman +2 more
TL;DR: An empirical algorithm for the retrieval of soil moisture content and surface root mean square (RMS) height from remotely sensed radar data was developed using scatterometer data and inversion results indicate that significant amounts of vegetation cause the algorithm to underestimate soil moisture and overestimate RMS height.
Journal ArticleDOI
Calibration of time domain reflectometry for water content measurement using a composite dielectric approach
TL;DR: In this paper, a calibration curve for the TDR method is presented which is not restricted to specific soil conditions, based on the dielectric mixing model of Dobson et al. (1985).
Journal ArticleDOI
Soil Moisture Measurement for Ecological and Hydrological Watershed-Scale Observatories: A Review
David A. Robinson,Colin S. Campbell,Jan W. Hopmans,Brian K. Hornbuckle,Scott B. Jones,Rosemary Knight,Fred L. Ogden,John S. Selker,Ole Wendroth +8 more
TL;DR: In this article, the authors review advances in sensor technology, particularly emerging geophysical methods and distributed sensors, aimed at bridging this gap and offer a vision for future research, listing many of the current scientific and technical challenges.
Journal ArticleDOI
The SMOS Soil Moisture Retrieval Algorithm
Yann Kerr,Philippe Waldteufel,P. Richaume,Jean-Pierre Wigneron,Paolo Ferrazzoli,A. Mahmoodi,Ahmad Al Bitar,Francois Cabot,C. Gruhier,S. Juglea,Delphine Leroux,Arnaud Mialon,Steven Delwart +12 more
TL;DR: A retrieval algorithm to deliver global soil moisture (SM) maps with a desired accuracy of 0.04 m3/m3 is given, discusses the caveats, and provides a glimpse of the Cal Val exercises.
References
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Journal ArticleDOI
An Empirical Model for the Complex Dielectric Permittivity of Soils as a Function of Water Content
James R. Wang,Thomas J. Schmugge +1 more
TL;DR: In this paper, a simple empirical model was proposed to describe the dielectric behavior of the soil-water mixtures and the model employed the mixing of either the Dielectric constants or the refraction indices of ice, water, rock and air, and treated the transition moisture value as an adjustable parameter.
Journal ArticleDOI
Dielectric properties of soils at UHF and microwave frequencies
P. Hoekstra,A. Delaney +1 more
TL;DR: In this article, the complex dielectric constant of four soils, including a sand, a silt, and two clays, was measured over the frequency range from 0.1 × 109 Hz to 26 ×109 Hz.
Journal ArticleDOI
Theory for passive microwave remote sensing of near‐surface soil moisture
Eni G. Njoku,Jin-Au Kong +1 more
TL;DR: In this article, a coherent stratified model is presented which is valid for nonuniform temperature profiles and rapidly varying moisture profiles, under which conditions the commonly used emissivity and radiative-transfer approaches become inaccurate.
Journal ArticleDOI
Soil electromagnetic parameters as functions of frequency, soil density, and soil moisture
TL;DR: In this article, the conductivity and dielectric constants of gray clay and a reddish-brown clay loam were determined as a function of soil density, soil moisture, and excitation frequency.
Journal ArticleDOI
Dielectric properties of soils at UHF and microwave frequencies
P. Hoekstra,A. Delaney +1 more
TL;DR: In this article, the complex dielectric constant of four soils, including a sand, a silt, and two clays, was measured over the frequency range from 0.1 × 109 Hz to 26 ×109 Hz.