土壤水分和大气干燥度影响全球范围内的蒸发蒸腾作用的时空变化，这一成果由丹麦哥本哈根大学Wenmin Zhang团队经过不懈努力而取得。相关论文于2023年2月25日发表在《JGR大气》杂志上。

研究人员使用FLUXNET数据库中的140个通量塔，对蒸发蒸腾作用产品的性能进行了评估。所有蒸发蒸腾作用产品均表现出合理的性能，总体相关系数均高于0.7，且在纬度越高的地区表现越好。从年蒸发蒸腾作用的集合均值分析，1982-2020年全球蒸发蒸腾作用变化趋势不显著(P = 0.06)，而2002-2020年间呈显著(P <0.01) 上升趋势。GLEAM 蒸发蒸腾作用的变化通常对土壤水分的变化具有正响应，对水汽压亏差的变化具有负响应。然而，这些影响在全球范围内并不一致，在很大程度上取决于植被蒸腾作用的变化。

以研究发现为基准，地球系统模型大多再现了耦合强度较小的蒸发蒸腾作用对土壤水分的正响应，而水汽压亏差对耦合强度较强的蒸发蒸腾作用的负响应。研究结果强调，同时发生的土壤干燥和大气干旱可以加强水分交换，以及在模型中真实地表示土壤湿度-水汽压亏差- 蒸发蒸腾作用对于准确预测水文循环的重要性。

据介绍，蒸发蒸腾作用(ET)构成了从陆地到大气的水交换，从而调节降水和土壤湿度。多行证据记录了蒸发蒸腾作用与温度、大气二氧化碳和植被绿化变化之间的复杂反馈。然而，现有的蒸发蒸腾作用对全球变化分析在考虑多个环境变量的同时，没有考虑土壤水分供给和大气需水的直接影响(以水汽压亏差(VPD)表示)。

附：英文原文

Title: Soil moisture and atmospheric aridity impact spatio-temporal changes in evapotranspiration at a global scale

Author: Wenmin Zhang, Julian Koch, Fangli Wei, Zhenzhong Zeng, Zhongxiang Fang, Rasmus Fensholt

Issue&Volume: 2023-02-25

Abstract: Evapotranspiration (ET) constitutes the water exchange from land to the atmosphere, which in turn modulates precipitation and soil moisture. Multiple lines of evidence document complex feedbacks between changes in ET and temperature, atmospheric CO₂ and vegetation greening. However, the existing analyses on global changes in ET do not account for the direct effects of soil moisture supply and atmospheric water demand, expressed by vapor pressure deficit (VPD), while considering multiple environmental variables. Here we evaluated the performance of ET products using 140 flux towers included in the FLUXNET database. All ET products show reasonable performance, with an overall correlation higher than 0.7 and better performance at a higher latitude. From analysis of the ensemble mean of annual ET, we show insignificant (P = 0.06) trends in global ET during 1982–2020 and a significantly (P < 0.01) increasing trend during 2002–2020. Changes in GLEAM ET generally exert a positive response to changes in soil moisture and a negative response to changes in VPD. Yet, these effects are not globally consistent and are largely determined by changes in vegetation transpiration. Using our finding as a benchmark, Earth System Models mostly reproduce the positive response of ET to soil moisture with less coupling strength, while showing negative effects of VPD on ET with stronger coupling strength. Our study highlights that concurrent soil drying and atmospheric aridity could intensify water exchanges and the importance of realistically representing soil moisture-VPD-ET interactions in models for accurate predictions of the hydrological cycle.

DOI: 10.1029/2022JD038046

Source: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JD038046