Evaluation of two strategies from the SEBS model for estimating the daily terrestrial evapotranspiration values of the Tibetan Plateau

• A comparison between two strategies for estimating daily evapotranspiratlon. • An analyzation of the performance of two strategies under different conditions. • Exploration of factors contributing to evapotranspiration at different time scales. The evapotranspiration (ET) of the Qinghai–Tibet Plateau (TP) has an essential role in regulating global atmospheric circulation. Daily ET values are usually estimated from the Surface Energy Balance System (SEBS) model in conjunction with the evaporative fraction invariant method (SEBS-INV). A growing number of studies use daily average factors to obtain daily-scale ecohydrological outcomes, while the use of daily average elements for daily ET estimations based on the SEBS model remains relatively unexplored. In this study, we conducted a comprehensive evaluation of the SEBS-INV strategy and the daily-scale SEBS model (SEBS-AVG) for estimating the daily ET over the TP region. The results indicate that the SEBS-INV yielded better daily ET values, with an average Coefficient of Determination (R 2 ) of 0.42 and the Kling-Gupta efficiency (KGE) of 0.5, while the average R 2 and KGE values for the SEBS-AVG were 0.34 and 0.37, respectively. It is noteworthy that the SEBS-AVG better captures the ET differences across vegetation types, especially in the Hengduan Mountain region. In the case of relative humidity (RH) > 70 %, the outputs of the two strategies exhibited similar performances. However, under water-limited conditions (RH<70%), the SEBS-AVG significantly overestimated the ET values. These overestimations can be attributed to the impact of model input uncertainties on the estimated scalar roughness height for heat transfer (z0h).