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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #411936
Research Project: From Field to Watershed: Enhancing Water Quality and Management in Agroecosystems through Remote Sensing, Ground Measurements, and Integrative Modeling

Location: Hydrology and Remote Sensing Laboratory

Title: Calculating a minimum overlap period for successful intercalibration of soil moisture sensors

Author
item WALKER, V - Orise Fellow
item Cosh, Michael
item OCHSNER, T - Oklahoma State University

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2024
Publication Date: 5/29/2024
Citation: Walker, V.A., Cosh, M.H., Ochsner, T. 2024. Calculating a minimum overlap period for successful intercalibration of soil moisture sensors. Vadose Zone Journal. 23(4). Article e20346. https://doi.org/10.1002/vzj2.20346.
DOI: https://doi.org/10.1002/vzj2.20346

Interpretive Summary: Soil moisture sensor technologies are constantly evolving or in need of replacement, but long time series data is critical for many applications. A study was conducted to determine what the minimum length of time is feasible and necessary to operate and original sensor installation in tandem with a new sensor installation so that a conversion equation can be developed for a harmonized long term product. The minimum time period was determined to be 6-9 months, with a full year being optimal. This work is of value to network operators who must plan for network upgrading and renovation.

Technical Abstract: Long-term in situ soil moisture monitoring inevitably requires sensors to be replaced. Ensuing discontinuities in the data record can be mitigated by intercalibration, however it is unclear how long the existing sensor needs to remain alongside the newly installed before there is enough overlapping data to generate a robust intercalibration. We used 224 pairs of established and newly installed sensors within the Marena, Oklahoma, In Situ Sensor Testbed (MOISST) to determine if there is a minimum overlap time that should be considered when planning upcoming replacements. Observations of the existing sensor were linearly calibrated to those of the newly installed sensor with coefficients determined from overlap periods incremented by thirty days until a reference period of two years was reached. The resulting bias, RMSE, and correlation coefficient for sensor pairs indicate that a minimum of six to nine months of overlapping data is required to generate a successful intercalibration. Extending that to a full year before decommissioning the old sensor results in a stable intercalibration with higher confidence.