Eric Embacher

Dielectric Relaxation of Bound Water versus Soil Matric Pressure

The dielectric permittivity of soil is a function of the water content, which facilitates water content measurements. The permittivity of soil is also a function of the frequency of the applied electric field. This frequency dependence can be described by the relationship between the dielectric relaxation frequency and the activation enthalpy of the water, which …

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Soil pH

Soil pH defines the relative acidity or alkalinity of the soil solution. The pH scale in natural systems ranges from 0 to 14. A pH value of 7.0 is neutral. Values below 7.0 are acid and those above 7.0 are alkaline, or basic. Many agricultural soils have a soil pH between 5.5 and 6.5. Soil …

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Coaxial Impedance Dielectric Reflectometry

The Coaxial Impedance Dielectric Reflectometry (also referred to as “Ratiometric Coaxial Impedance Dielectric Reflectometry”) method of soil moisture measurement employs an oscillator to generate an electromagnetic signal that is propagated through the sensor by metal tines and into the soil. It characterizes the ratio of the amplitudes of reflected radio waves at 50 MHz with a …

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Capacitance (Charge)

Capacitance determines the dielectric constant (Ka) by measuring the charge time of a capacitor, which uses soil as a dielectric medium. The charge time of the capacitor is a linear function of the dielectric permittivity of the soil. Capacitance sensors measure the dielectric constant of the soil in order to find its water content. Since the dielectric constant of water …

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Frequency Domain Reflectometry (FDR) / Capacitance (Frequency)

Capacitance can be measured from the change in frequency of a reflected radio wave or resonance frequency (Kelleners 2004). This method of measurement uses an oscillator to propagate an electromagnetic signal through a metal tine or other wave guide. The difference between the output wave and the return wave frequency is measured to determine soil …

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McMaster Mesonet soil moisture dataset: Description and spatio-temporal variability analysis

This paper introduces and describes the hourly, high-resolution soil moisture dataset continuously recorded by the McMaster Mesonet located in the Hamilton-Halton Watershed in Southern Ontario, Canada. The McMaster Mesonet consists of a network of time domain reflectometer (TDR) probes collecting hourly soil moisture data at six depths between 10 cm and 100 cm at nine …

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ENSO–cave drip water hydrochemical relationship: a 7-year dataset from south-eastern Australia

Speleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water …

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The effects of fire on the thermal stability of permafrost in lowland and upland black spruce forests of interior Alaska in a changing climate

Fire is an important factor controlling the composition and thickness of the organic layer in the black spruce forest ecosystems of interior Alaska. Fire that burns the organic layer can trigger dramatic changes in the underlying permafrost, leading to accelerated ground thawing within a relatively short time. In this study, we addressed the following questions. …

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The NOAA Hydrometeorology Testbed Soil Moisture Observing Networks: Design, Instrumentation, and Preliminary Results

The NOAA Hydrometeorology Testbed (HMT) program has deployed soil moisture observing networks in the watersheds of the Russian River and the North Fork (NF) of the American River in northern California, and the San Pedro River in southeastern Arizona. These networks were designed to serve the combined needs of the hydrological, meteorological, agricultural, and climatological …

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SMAP (Soil Moisture Active Passive) Handbook: Mapping Soil Moisture and Freeze/Thaw from Space

Soil moisture is a primary state variable of hydrology and the water cycle over land. In diverse Earth and environmental science disciplines, this state variable is either an initial condition or a boundary condition of relevant hydrologic models. Applications such as weather forecasting, skillful modeling and forecast of climate variability and change, agricultural productivity, water …

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