*2.4. Verification Experiment*

The Bowen ratio energy balance (BREB) method was used as the benchmark to verify the '3T + IR' method. The verification experiment was conducted before the field experiments, on three sunny

days (15 July 2014, 16 August 2014, and 13 November 2014). The ET rates of the studied area were simultaneously measured by the '3T + IR' method and the BREB method. The ET rates by the BREB method could be calculated by [53]

$$ET = \frac{R\_n - G}{L(1 + \beta)}\tag{5}$$

$$
\beta = \frac{\mathcal{C}\_p \Delta T}{L \Delta q} \tag{6}
$$

where *L* is the latent heat of water vaporization (J kg−1), *G* is the soil heat flux (W m<sup>−</sup>2), *β* is the Bowen ratio, *Cp* is the specific heat of air at a constant pressure (J kg−<sup>1</sup> ◦C−1), and Δ*T* and Δ*q* are the temperature and humidity difference between the heights of 2.0 m and 1.5 m, respectively. All these parameters were obtained by the Bowen ratio system.
