AGU: Geophysical Research Letters

 

Editors' Highlight

A new noninvasive way to measure soil moisture

Because of its long residence time, soil moisture moderates regional climate much like the ocean does, making quantifications of soil moisture critical for weather and short-term climate forecasting. However, measuring soil moisture is difficult because point measurements must be extrapolated to larger areas, introducing significant error, and because satellite remote sensors have difficulty penetrating surface cover. To move past these difficulties, Zreda et al. (2008) developed a new, noninvasive technique that infers soil moisture content from measurements of low-energy cosmic ray neutrons that are generated within soil, moderated mainly by hydrogen atoms, and diffused back to the atmosphere. These neutrons are sensitive to water content changes but do not fluctuate with changes in soil chemistry. Further, their intensity above the surface is inversely correlated with hydrogen content in the soil. By placing a portable neutron detector a few meters above the ground, the authors generated high-resolution, long-term records of undisturbed soil moisture conditions over an area about 700 m in diameter. This method will be valuable for calibrating satellites, studying plant/soil interaction and atmosphere/soil exchange, and initializing soil moisture conditions for short-term weather and climate forecasts.

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