Testing the Rationale behind an Assumed Linear Relationship between Evapotranspiration and Land Surface Temperature

Theoretical considerations and empirical evidence indicate a linear relationship between the land surface temperature (Ts) and the corresponding evapotranspiration (ET) rate under spatially constant wind and net energy conditions at a homogeneous vegetated surface. Such a relationship lies at the core of the popular surface energy balance algorithm (SEBAL); the satellite-based energy balance approach for mapping evapotranspiration with internalized calibration (METRIC); and the lesser known calibration-free evapotranspiration mapping (CREMAP) method, just to name a few. The present findings are based on analytical solutions of the coupled turbulent heat and vapor transport equations and further corroborated by monthly reanalysis data of Ts, ET, and sensible heat transfer rates over extensive areas in North America and Europe, where the CREMAP method has previously been applied. DOI: 10.1061/(ASCE)HE.1943-5584.0001091. © 2014 American Society of Civil Engineers. Author keywords: Remote sensing; Vegetated land; Surface temperature; Linear relationship; Evapotranspiration.