Evaluation of evapotranspiration models over semi-arid and semi-humid areas of China

Evapotranspiration (ET) is a critical component in the hydrological cycle. However, its actual values appear to be difficult to obtain, especially in areas in which precipitation has high inter-annual variability. Here, we evaluated eight commonly used ET models in semi-arid and semi-humid areas of China. The order of overall performance from best to worst is as follows: the revised Priestley-Taylor model (PT-JPL, 0.71, 1.65 [18.37%], 4.72 [49.19%]), the modified PT-JPL model (M1-PT-JPL, 0.67, -0.68 [7.56%], 3.87 [40.31%]), the Community Land Model (CLM, 0.68, -2.52 [28.01%], 5.10 [53.17%]), the modified PT-JPL model (M2-PT-JPL, 0.63, 0.57 [6.27%], 5.04 [52.52%]), the revised Penman-Monteith model (RS-PM, 0.62, 3.56 [37.40%], 6.11 [63.68%]), an empirical model (Wang, 0.59, -1.04 [11.57%], 5.61 [58.43%]), the advection-aridity model (AA, 0.55, 5.56 [61.78%], 7.45 [77.60%]), and the energy balance model (SEBS, 0.35, 5.11 [56.72%], 9.43 [98.18%]). The performance of all of the models is comparably poor in winter and summer, except for the PT-JPL model, and relatively good in spring and autumn. Because of the vegetation control on ET, the Wang, RS-PM, PT-JPL, M1-PT-JPL, and M2-PT-JPL models perform better for cropland, whereas the AA model, SEBS model and CLM perform better for grassland. The CLM, PT-JPL, and Wang models perform better in semi-arid region than in semi-humid region, whereas the opposite is true for SEBS and RS-PM. The AA, M1-PT-JPL, and M2-PT-JPL models perform similarly in semi-arid and semi-humid regions. When considering the inter-annual variability in precipitation, the Wang model has relatively good performance under only some annual precipitation conditions; the performance of the PT-JPL and AA models is reduced under conditions of high precipitation; the two modified PT-JPL models inherited the steady performance of the PT-JPL model and improved the performance under conditions of high annual precipitation by the modification of the soil moisture constraint. RS-PM is more appropriate for humid conditions. CLM and PT-JPL models could be effectively applied to all precipitation conditions because of their good performance across a wide annual precipitation range. Copyright (c) 2016 John Wiley & Sons, Ltd.