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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 #391698
Research Project: Integrating Remote Sensing, Measurements and Modeling for Multi-Scale Assessment of Water Availability, Use, and Quality in Agroecosystems

Location: Hydrology and Remote Sensing Laboratory

Title: Can surface soil moisture information identify landscape evapotranspiration regime transitions

Author
item DONG, J. - Massachusetts Institute Of Technology
item AKBAR, R. - Massachusetts Institute Of Technology
item GIANOTTI, D. - Massachusetts Institute Of Technology
item FELDMAN, A. - Massachusetts Institute Of Technology
item Crow, Wade
item ENTEKHABI, D. - Massachusetts Institute Of Technology

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2022
Publication Date: 4/5/2022
Citation: Dong, J., Akbar, R., Gianotti, D., Feldman, A., Crow, W.T., Entekhabi, D. 2022. Can surface soil moisture information identify landscape evapotranspiration regime transitions. Geophysical Research Letters. 49:e2021GL097697. https://doi.org/10.1029/2021GL097697.
DOI: https://doi.org/10.1029/2021GL097697

Interpretive Summary: Crop evapotranspiration (ET) can be limited by either soil water availability or the evaporative demand of the lower atmosphere. During interstorm dry downs, agricultural fields transition from one regime to another. Understanding this transition has important consequences for irrigation management, fertilizer application strategies and crop-yield forecasting. Soil moisture (SM) retrievals based on microwave remote sensing is a potentially useful tool for analyzing transitions in large-scale ET regimes. However, microwave signals are mainly sensitive to surface soil moisture (SSM), which is not representative of root-water uptake from the entire crop rootzone. Therefore, the applicability of remotely sensed SSM information for ET regime identification is uncertain. In this study, we use flux tower, surface and vertically integrated in-situ SM observations to examine the reliability of SSM for ET regime identification. Results demonstrate that SSM and vertically integrated observations are equivalently skillful for identifying the percentage of time a given landscape spends in the water-limited ET regime. Therefore, remotely sensed SSM retrievals can be used to robustly identify ET regime changes in agricultural regions around the world.

Technical Abstract: The transition of evapotranspiration between energy- and water-limitation regimes also denotes a nonlinear change in surface water and energy coupling strength. The regime transition is dominated by available moisture in the soil. Remotely sensed soil moisture is frequently used for detecting evapotranspiration regime transitions during interstorm drydowns. However, its sampling depth does not include the entire soil profile, over which water uptake is dominated by plant root distribution. We use flux tower, surface (SSM, observations at 5 cm) and vertically-integrated in-situ soil moisture (VSM, 0 to 50 cm) observations to address the question: can SSM robustly identify evapotranspiration regime transitions? Results demonstrate that SSM and VSM capture comparable statistics of evapotranspiration regime prevalence. A hypothesis for the consistency of SSM- and VSM-based evapotranspiration regime identification is proposed and verified. Therefore, SSM (e.g., obtained via global scale remote sensing) is valuable for identifying evaporation regime transitions