SEDL / STP / STP1358-EB / STP14227S

Remote Field Methods to Measure Frost Depth

Benson, CH
Associate Professor, University of Wisconsin-Madison, Madison, WI

Bosscher, PJ
Professor, University of Wisconsin-Madison, Madison, WI

Pages: 18    Published: Jan 1999

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Abstract

This paper reviews the three common methods used to remotely measure frost depth: (1) soil temperature measurements, (2) soil electrical resistivity measurements, and (3) soil dielectric constant measurements. Soil temperature measurements are often made using thermocouples or thermistors. Specially designed probes are used to measure frost depth based on electrical resistivity. Inferences based on dielectric constant are usually made using time domain reflectometry. Frost depths based on soil temperatures are made equally well using thermistors or thermocouples. However, frost depths inferred from soil temperature measurements can be erroneous if the freezing point is depressed (due to unsaturated conditions or the presence of salts) or if the temperature profile is essentially isothermal and near 0°C. More reliable measurements of frost depth are made using electrical resistivity or dielectric constant measurements because the electrical properties of soil are affected more by phase change of the pore water than temperature.