Resolving Heat Pulse Measurement Anomalies.

The process of soil evaporation is of significance for a wide range of disciplines interested in monitoring and management of the soil hydrologic regime. Applications are found in agricultural, environmental, meteorological, ecological and industrial sectors spanning from point- to watershed-scales and beyond. Hexa-needle and penta-needle heat pulse probes (HPP) are designed to in-situ measure soil temperature and thermal properties (i.e., thermal conductivity and thermal diffusivity), providing an effective means to calculate subsurface soil-water evaporation rates. In addition, the soil water content at the receding drying front is estimated as a function of soil heat capacity and bulk density. While preliminary HPP data show promise, a thorough evaluation of differences between calculated evaporation rates and soil water contents with numerical simulations is lacking. Due to the geometric constraints imposed in the heat pulse method, thermal properties cannot be measured directly for all near-surface layers. As a result, thermal properties for constituent layers were resolved using the depth-weighted harmonic mean. However, this approach did not yield consistent results. Moreover, some discrepancies have been observed with needle-spacing calibration, which directly affects  thermal property estimates. In our presentation we discuss potential solutions to resolve anomalies encountered with the heat pulse method.

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See more from this Division: SSSA Division: Soil Physics
See more from this Session: Advancing Measurement Technology in Soil and Environmental Physics: An Original Research Instrumentation Showcase (includes student competition)

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