Evaluation of a Two-Layer Model to Estimate Vine Transpiration and Soil Evaporation for Vineyards

The two-layer model of Shuttlerworth and Wallace (SW) was evaluated to estimate vine transpirationa (Tsw) and soil evaporation (Esw) from a drip-irrigated Merlot vineyard, located in the Talca Valley, Region del Maule, Chile (35° 25' LS; 71° 32' LW; 136m above the sea level). An automatic weather system was installed in the center of the vineyard to measure air temperature, relative humidity, wind speed, solar radiation and latent heat flux during January 2007. Values of Tsw and Esw were compared to sap flow and microlysimeter measurements, respectively. Also, vineyard evapotranspiration (ETsw) computed by the SW model was evaluated using latent heat flux measurements obtained from an eddy-covariance system on a 30 minute time interval. Results indicated that SW model was able to predict vineyard evapotranspiration with a root mean square error (RMSE) of 0.3 mm day–1. Also, SW model predicted soil evaporation and vine transpiration with RMSE of 0.2 and 0.8 mm day–1, respectively. In general, the SW model tended to underestimate transpiration and vineyard evapotranspiration, and overestimate the soil evaporation.