Accurate estimation of global evapotranspiration (ET) is critical to understand the water and energy cycles in the Earth system. Satellite-driven ET algorithms serve as an effective way to estimate the global ET. However, many algorithms have been designed independently of water balance constraints, which potentially limit their ability to estimate ET in water-limited and high interception regions. As ET remains one of the most uncertain terms in the global water budgets, incorporating water balance constraints into algorithms should improve the performance of ET estimates. In this study, we developed a general solution (denoted PEW) based on the proportionality hypothesis to incorporate available water control into the widely used Priestley Taylor-Jet Propulsion Laboratory (PT-JPL) ET algorithm. Simulated performances of the PEW model and PT-JPL algorithm were evaluated against 106 FLUXNET eddy covariance (EC) towers data at the site scale. Meanwhile, model results were compared at the global scale with the means of the widely used ET products. We found that the PEW model has smaller errors than the original PT-JPL algorithm, with the greatest improvements in water-limited regions and areas characterized by the high interception. Moreover, by incorporating the water balance constraints into the ET algorithm, the PEW model has the ability to distinguish variations in ET affected by El Nino-Southern Oscillation. In summary, our study offers a convincing evidence regarding the incorporation of water balance constraints into remote sensing algorithms for more accurately mapping global terrestrial ET with an enhanced understanding of ET variation under climate change. This model is the first of its kind among remote-sensing models to provide global land ET estimation with the proportionality hypothesis-based water balance constraints.

准确估计全球蒸发量 (ET) 对于了解地球系统中的水和能量循环至关重要。卫星驱动的 ET 算法是估计全球 ET 的有效方法。然而，许多算法的设计独立于水平衡约束，这可能会限制它们在水受限和高截流区域估计 ET 的能力。由于 ET 仍然是全球水预算中最不确定的术语之一，将水平衡约束纳入算法应该会提高 ET 估计的性能。在这项研究中，我们基于比例假设开发了一个通用解决方案（表示为 PEW），以将可用的水控制纳入广泛使用的 Priestley Taylor-Jet Propulsion Laboratory (PT-JPL) ET 算法。PEW 模型和 PT-JPL 算法的模拟性能在站点规模上针对 106 个 FLUXNET 涡度协方差 (EC) 塔数据进行了评估。同时，模型结果在全球范围内与广泛使用的ET产品的手段进行了比较。我们发现PEW模型的误差比原始的PT-JPL算法的误差更小，在限水区域和高截断区域的改进最大。此外，通过将水平衡约束纳入 ET 算法，PEW 模型能够区分受厄尔尼诺-南方涛动影响的 ET 变化。总之，我们的研究提供了一个令人信服的证据，即将水平衡约束纳入遥感算法，以便更准确地绘制全球陆地 ET 地图，增强对气候变化下 ET 变化的理解。该模型是遥感模型中第一个提供具有基于比例假设的水平衡约束的全球陆地 ET 估计的模型。