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A simple and objective method to partition evapotranspiration into transpiration and evaporation at eddy-covariance sites

机译:一种简单且客观的方法,将蒸散分化为涡旋间位点的蒸发和蒸发

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Separating evapotranspiration (ET) into evaporation (E) and transpiration (7) is challenging but key for a better understanding and prediction of the hydrological cycle and plant water use. In this study, flux data at 30 routine eddy-covariance sites were used to develop a new and simple method for ET partitioning based on the separation of soil and canopy conductances, with the main assumption that the latter is proportional to gross primary productivity (GPP). The result of T:ET across different plant functional types (PFTs) was consistent with recent modeling or empirical results. The mean annual T:ET was highest for evergreen needleleaf forests (0.75 +/- 0.17), followed by croplands (0.62 +/- 0.16) and grasslands (0.56 +/- 0.15). The leaf area index (LAI) was shown to explain only small (20%) variations of mean annual T:ET across sites. However, at each site, the correlation of T:ET with LAI was strong at the seasonal scale, where T:ET increased nonlinearly with LAI. The results did not show significant relationship of T:ET with long-term mean precipitation across sites at multiyear timescales. However, the partitioned soil evaporation after each precipitation pulse is consistent with three-stage soil evaporation theory. This ET partitioning method is an objective assessment as it is mainly data-driven. The procedure to apply this method is also simple so it can be readily applied to global flux tower networks at different temporal and spatial scales, enabling continuous estimation of T:ET to monitor ecosystem dynamics and hydrological responses to environmental change.
机译:将蒸发(ET)分离成蒸发(e)和蒸腾(7)是挑战,但更好地理解和预测水文循环和植物用水的关键。在本研究中,基于土壤和冠层导电的分离,使用30个常规涡流位点的助焊剂数据在分离土壤和冠层导电的情况下开发新的和简单的ET分配方法,其中后者与初级生产率成比例(GPP )。不同植物功能类型(PFT)的T:et的结果与最近的建模或经验结果一致。常青树的森林(0.75 +/- 0.17),常绿的森林(0.75 +/- 0.16)和草原(0.56 +/- 0.15)。叶面积指数(LAI)显示仅解释平均年度的少数(20%)变化:ex跨地网站。然而,在每个站点,T:ET与Lai的相关性在季节性范围内强烈,其中T:ET与Lai非线性增加。结果没有表现出T:ET在多年时间尺度的长期平均沉淀的显着关系。然而,每个沉淀脉冲后分配的土壤蒸发与三级土壤蒸发理论一致。该ET分区方法是一种客观评估,因为它主要是数据驱动。应用该方法的程序也很简单,因此可以容易地应用于不同时间和空间尺度的全局助焊塔网络,从而能够连续估计T:ET,以监测生态系统动态和对环境变化的水文反应。

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