Abstract

The aim of this research was to evaluate the clumped model for estimating latent heat flux (LE) and actual evapotranspiration (ETa) over a non-water-stressed olive orchard. Additionally, submodels to compute the net radiation R-n, soil heat flux G, and canopy resistance were also included. For this objective, a database was used from an experimental unit inside a commercial superintensive drip-irrigated olive orchard located in the Pencahue Valley, Maule Region, Chile (35 degrees 23 ' S, 71 degrees 44 ' W; 96 m above sea level) during the 2009/10 and 2010/11 growing seasons. The evaluation was carried out using measurements of LE obtained from an eddy covariance (EC) system. In addition, estimated values of R-n, G, and were compared with ground-truth measurements from a four-way net radiometer, soil heat flux plates with soil thermocouples, and a portable porometer, respectively. Results indicated that the clumped model underestimated LE and ETa with errors of 11.0% and 3.0%, respectively. Values of the root-mean-square error (RMSE), mean bias error (MBE), and index of agreement d(r) for LE were 35 W m(-2), -1.0 W m(-2), and 0.96, while those for ETa were 0.48 mm day(-1), 0.04 mm day(-1), and 0.64, respectively. The submodels computed R-n and G with errors less than 6% and RMSE values less than 65 W m(-2), while the Jarvis-type model predicted with RMSE = 41 s m(-1) and MBE = 7.0 s m(-1). Finally, a sensitivity analysis indicated that the ETa estimated by the clumped model was significantly affected by variations of +/- 30% in the values of the LAI and the minimum stomatal resistance r(stmin).