Examination of the Bowen ratio energy balance technique for evapotranspiration estimates in screenhouses

For the first time, the applicability of the Bowen ratio energy balance technique to evapotranspiration estimates in screenhouses was investigated. Measurements were conducted at the centre of a large banana screenhouse in northern Israel. Data of eddy covariance flux measurements and vertical temperature and humidity gradients were used to estimate the ratio between the turbulent transport coefficients of heat and water vapour. Data from 8 days were used for calibration, and those from an additional 4 days for validation of the method. Calibration results showed that the ratio between the turbulent transport coefficients was close to unity during most daytime hours, indicating that the method is applicable in the screenhouse environment. The Bowen ratio was nearly constant during most daytime hours, with an average of 0.41 ± 0.07. During the validation period, very good agreement was obtained between the latent heat flux as estimated with the Bowen ratio method and that deduced from EC measurements.