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In Situ Thermistor Calibration for Improved Measurement of Soil Temperature Gradients
Author(s) -
Kool Dilia,
Heitman Joshua L.,
Lazarovitch Naftali,
Agam Nurit,
Sauer Thomas J.,
Ben-Gal Alon
Publication year - 2016
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2016.05.0134
Subject(s) - thermistor , calibration , environmental science , flux (metallurgy) , temperature measurement , heat flux , in situ , soil science , materials science , latent heat , atmospheric sciences , meteorology , heat transfer , geology , thermodynamics , geography , statistics , physics , mathematics , electrical engineering , metallurgy , engineering
Core Ideas Soil temperature gradients are important for soil (latent) heat flux estimation. Heat‐pulse sensor thermistors' temperature differences were on the order of 0.2°C. In situ calibration reduced uncertainty between thermistors to about 0.06°C. In situ calibrated offsets between thermistors were similar to laboratory results. Offsets were found to change very little over a 5‐yr period. Accurate measurement of soil temperature gradients is important for the estimation of soil heat flux and latent heat flux, both major components of the surface energy balance. Soil temperature gradients are commonly measured using heat‐pulse sensors equipped with thermistors. In this study, individual thermistors showed absolute temperature differences on the order of 0.2°C when placed under uniform temperature conditions. These differences compromised measurement of soil temperature gradients over small depth increments and/or conditions with relatively minor variation in temperatures. An in situ calibration approach was found to reduce the uncertainty between thermistors to about 0.05°C in a vineyard under arid conditions. In situ calibration results were similar to laboratory results before and after field deployment for temperatures ranging between 4 and 60°C. Thermistor offsets were found to change very little over a 5‐yr period, indicating that pre‐ or post‐laboratory calibration could be sufficient. The in situ approach can be useful when calibration prior to field deployment is unavailable and/or sensor failure prevents post‐field calibration.