Bridging Thermal Infrared Sensing and Physically-Based Evapotranspiration Modeling: From Theoretical Implementation to Validation Across an Aridity Gradient in Australian Ecosystems

Kaniska Mallick*, Erika Toivonen, Ivonne Trebs, Eva Boegh, James Cleverly, Derek Eamus, Harri Koivusalo, Darren Drewry, Stefan K Arndt, Anne Griebel, Jason Beringer, Monica Garcia

*Corresponding author for this work

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Abstract

Thermal infrared sensing of evapotranspiration (E) through surface energy balance (SEB) models is challenging due to uncertainties in determining the aerodynamic conductance (gA) and due to inequalities between radiometric (TR) and aerodynamic temperatures (T0). We evaluated a novel analytical model, the Surface Temperature Initiated Closure (STIC1.2), that physically integrates TR observations into a combined Penman‐Monteith Shuttleworth‐Wallace (PM‐SW) framework for directly estimating E, and overcoming the uncertainties associated with T0 and gA determination. An evaluation of STIC1.2 against high temporal frequency SEB flux measurements across an aridity gradient in Australia revealed a systematic error of 10% – 52% in E from mesic to arid ecosystem, and low systematic error in sensible heat fluxes (H) (12% – 25%) in all ecosystems. Uncertainty in TR versus moisture availability relationship, stationarity assumption in surface emissivity, and SEB closure corrections in E were predominantly responsible for systematic E errors in arid and semi‐arid ecosystems. A discrete correlation (r) of the model errors with observed soil moisture variance (r = 0.33 to 0.43), evaporative index (r = 0.77 to 0.90), and climatological dryness (r = 0.60 to 0.77) explained a strong association between ecohydrological extremes and TR in determining the error structure of STIC1.2 predicted fluxes. Being independent of any leaf‐scale biophysical parameterization, the model might be an important value addition in working group (WG2) of the Australian Energy and Water Exchange (OzEWEX) research initiative which focuses on observations to evaluate and compare biophysical models of energy and water cycle components.
Original languageEnglish
JournalWater Resources Research
Volume54
Issue number5
Pages (from-to)3409-3435
Number of pages27
ISSN0043-1397
DOIs
Publication statusPublished - 2018

Bibliographical note

This is an open access article under theterms of the Creative CommonsAttribution-NonCommercial-NoDerivsLicense, which permits use anddistribution in any medium, providedthe original work is properly cited, theuse is non-commercial and no modifi-cations or adaptations are made.

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