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Vegetation index-based partitioning of evapotranspiration is deficient in disturbed systems
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  • Pushpendra Raghav,
  • Pradeep Wagle,
  • Mukesh Kumar,
  • Tirtha Banerjee,
  • James P.S. Neel
Pushpendra Raghav
University of Alabama, Tuscaloosa
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Pradeep Wagle
USDA-ARS, Grazinglands Research Laboratory
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Mukesh Kumar
University of Alabama

Corresponding Author:mkumar4@eng.ua.edu

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Tirtha Banerjee
University of California, Irvine
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James P.S. Neel
USDA-ARS, Grazinglands Research Laboratory
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Partitioning evapotranspiration (ET) into its primary components, i.e., evaporation (E) and plant transpiration (T), is needed in a range of hydrometeorological applications. Using vegetation index (VI) to obtain spatially resolved T:ET ratio over large areas has emerged as a promising approach in this regard. Here, we assess the effectiveness of this approach in differently managed wheat systems. Results show a weak relation between T:ET and VI in disturbed (i.e., grazed) systems. Flux partitions based on a canonical T:ET vs. VI relation or one derived in a neighboring undisturbed wheat system introduce large errors in disturbed systems, thus underscoring the limits on the transferability of the VI-based ET partitioning approach. The effectiveness of the VI-based approach is found to be related to the strength of correlation between VI and vapor pressure deficit and/or radiation. This correlation metric can help identify settings where the approach is likely to be effective.