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United States Department of Agriculture

Agricultural Research Service

Title: Impedance Probe Calibration and Large Scale Soil Moisture Estimation During the Smex Experiments

Authors
item Cosh, Michael
item Jackson, Thomas
item Bindlish, Rajat - SSAI
item Famiglietti, James - UNIV. OF CA-IRVINE
item Ryu, Dongryeol - UNIV. OF CA-IRVINE

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2005
Publication Date: May 24, 2005
Citation: Cosh, M.H., Jackson, T.J., Bindlish, R., Famiglietti, J., Ryu, D. 2005. Impedance probe calibration and large scale soil moisture estimation during the SMEX Experiments [abstract]. Joint Assembly of the American Geophysical Union. 86(18):H33C-04.

Technical Abstract: Large-scale soil moisture estimates are important for hydrologic modeling and agricultural remote sensing applications. For soil moisture monitoring, gravimetric soil moisture sampling is reliable; however, it requires a significant investment to gather and process samples. Portable impedance probes serve as a valuable alternative to destructive gravimetric sampling. These probes measure the dielectric properties of the soil-water-air mixture from which the volumetric soil moisture can be inferred. As part of recent large-scale experiments in the summers of 2002, 2003, and 2004, three different methods for calibrating impedance probes were investigated with the support of coincident gravimetric samples. Field specific calibration improved the accuracy of the probe from greater than +/- 5% volumetric soil moisture to less than +/- 4%. In addition, a significant amount of bias was eliminated, sometimes greater than 8% in an individual field of study. It was also concluded field specific calibration removes a bias due to bulk density variations. Based upon these results it was determined that the generalized calibration is adequate for estimation of diverse conditions when considering large-scale phenomenon. For studies with more stringent accuracy requirements, however, field specific calibrations is necessary because of the reduction in bias and error.

Last Modified: 12/19/2014
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