Parameterization of a two-layer model for estimating vineyard evapotranspiration using meteorological measurements

The Shuttleworth and Wallace (SW) model with variable canopy resistance was evaluated to estimate evapotranspiration (ETv) from a drip-irrigated Merlot (Vitis vinifera L.) vineyard trained on a vertical shoot-positioned (VSP) system. This vineyard is located in the Talca Valley, Region del Maule, Chile (35°25′ LS; 71°32′ LW; 125 m a.s.l). The performance of the SW model was evaluated using the eddy-covariance method on a 30 min time interval. Also, sub-models to estimate net radiation (Rn) and soil heat flux (G) were used in the SW model. A good agreement between observed and estimated values of Rn was found with a root mean square error (RMSE) of 33 W m−2 and a mean absolute error (MAE) of 24 W m−2. Also, the SW model was able to estimate latent heat flux with RMSE and MAE of 34 and 21 W m−2, respectively. On a daily basis, results indicate that the SW model was able to predict the ETv with RMSE and MAE values of 0.51 and 0.41 mm d−1, respectively. These results suggest that it is possible to directly estimate ETv over unstressed grapevines using meteorological data and soil moisture measurements.