蒸发是全球水循环、能量循环和碳循环之间的重要纽带。深入理解蒸发机理、准确估算蒸发量及其变化趋势，对探究水循环过程机制、合理评估与利用淡水资源等方面具有重要的理论意义与实践价值。蒸发的合理估算依赖于对蒸发过程的准确理解。潜在蒸发作为实际蒸发的上限，是蒸发过程理解和模型估算的核心变量。潜在蒸发定义为下垫面水分供应充足时的实际蒸发量。然而，现有潜在蒸发模型的估算结果往往与潜在蒸发的物理定义不相符。这主要是因为现有的潜在蒸发估算模型以观测的气象变量作为模型输入，而气象变量的观测常常不符合潜在蒸发对湿润环境条件的客观要求。这一问题背后深层次的原因在于，传统蒸发理论及模型均以辐射和温度作为蒸发的外部驱动，而忽略了蒸发?辐射−温度间的耦合互馈作用。针对该问题，本论文基于最大蒸发理论解决了长久以来潜在蒸发估算中的难题。最大蒸发理论通过解析蒸发、辐射、温度间的耦合互馈关系，揭示了在水面温度升高的过程中，蒸发随温度变化出现的最大值即为水面蒸发。在此基础上，本论文进一步在湿润陆表上解析了蒸发?辐射−温度间的耦合互馈关系，基于水面最大蒸发理论发展了适用于湿润陆地表面的最大蒸发模型，首次在全球范围内计算了符合物理定义的潜在蒸发强度，并揭示了传统模型在估算潜在蒸发时的误差来源。基于上述对蒸发?辐射−温度间耦合关系的认识及潜在蒸发模型的发展，本文进一步完善了蒸发互补理论与模型。蒸发互补理论直接依赖于潜在蒸发对实际蒸发进行估算。然而，在当前的蒸发互补模型中，潜在蒸发的估算结果存在与其物理定义不相符的问题。更为关键的是，传统蒸发互补理论中仅考虑了陆面干湿变化过程中陆气间水汽和温度的互馈，而忽略了辐射的变化。针对该问题，本文充分考虑了陆气间水汽、温度和辐射在下垫面干湿变化过程中的互馈过程，基于最大蒸发模型估算符合物理定义的潜在蒸发，完善了蒸发互补过程机制，并发展了物理机制明晰且无需参数率定的蒸发互补模型。验证结果表明，本文建立的蒸发互补模型较传统蒸发模型有着更高的蒸发估算精度。进一步地，本文基于所建立的蒸发互补模型量化了全球陆面2001-2022年的实际蒸发量，并对其时空演变特征进行了分析。
Evaporation is a crucial linkage between water, energy and carbon cycles. In order to comprehend the mechanisms of the water cycle and effectively manage water resources, it is crucial to gain a thorough understanding of evaporation mechanisms and accurately estimate both the rate and trend of evaporation. The accurate estimation of evaporation depends on a comprehensive understanding of the evaporation process. Potential evaporation, as the upper limit of actual evaporation, is the core variable in understanding the evaporation process and estimating evaporation values. Potential evaporation is defined as the evaporation that would occur with an unlimited supply of water. However, the calculation of potential evaporation has a long-standing problem conflicting with its physical definition. This problem arises from the fact that meteorological forcings employed in conventional models, which are observed under actual conditions, are typically not saturated. The underlying reason lies in the traditional methods, which primarily regard radiation and temperature as external forcings in estimating evaporation, while failing to adequately consider the coupling among evaporation, radiation, and temperature. Addressing this concern, this dissertation utilizes the maximum evaporation theory to resolve the challenges in potential evaporation estimation. Recognizing the interdependence between evaporation, radiation, and temperature, the maximum evaporation theory reveals that the naturally occurring maximum evaporation value during water surface temperature increase aligns with the evaporation from the water surface. Based on the maximum evaporation theory for water surfaces, this dissertation explores the coupling between evaporation, radiation, and temperature on saturated land surfaces, as well as develops a maximum evaporation model suitable for such wet environments. Employing this model, this dissertation computes the global potential evaporation following its physical definition and sheds light on the underlying sources of error inherent in traditional models for potential evaporation estimation.Based on the understanding of the coupling relationship between evaporation, radiation, and temperature, and the development of potential evaporation model, this dissertation further enhances the theory and models of the complementary relationship theory, which relies on potential evaporation as a key input for estimating actual evaporation. However, in current complementary relationship approaches, there remains a mismatch between the estimated results and the physical definition of potential evaporation. More importantly, traditional complementary relationship methods only take into account the feedback of land-atmosphere humidity and temperature on surface moisture conditions, while neglecting the variations in radiation. To solve the above problems, this dissertation thoroughly examines the feedback of land-atmosphere humidity, temperature, and radiation on surface moisture. Employing the maximum evaporation model to achieve a more reasonable estimation of potential evaporation enhances our understanding of the complementary mechanism. Additionally, a physically-based and calibration-free complementary relationship model is developed. The performance of this model is validated, demonstrating higher accuracy in estimating evaporation compared to traditional models. Furthermore, leveraging the developed complementary relationship model, this dissertation quantified the actual evaporation over global land surfaces from 2001 to 2022 and analyzed its spatiotemporal evolution characteristics.
