Accurate determination of actual evapotranspiration (ETa) is important in various research fields like hydrology, meteorology, ecology and agriculture. In situ ETa can be determined using weighing lysimeters and eddy covariance. However, despite being regarded as the most precise in situ method for measuring ETa, the information content of lysimeter measurements remains poorly understood. Here we examined the spatial correlations between ETa measured at different locations by lysimeter (ET-LYS) and at different locations by eddy covariance (ET-EC). This was done for the period 2015 - 2020 and the analysis was made for different spatial (range: 0 to 500 km) and temporal scales (range: 1 day to 1 year) using 23 lysimeters and 4 eddy covariance towers. We found that: (a) Same lysimeters at the plot scale show very high correlations of ET-LYS; (b) The Pearson correlation of daily standardized anomalies of ET-LYS between sites exhibit moderate to high correlations and were similar to that of ET-EC, indicating that lysimeter is generally as representative as EC regarding ETa, and can provide certain information at the landscape and larger regional scale. During winter, the spatial correlations for ET-LYS were smaller; (c) Wavelet analysis indicated that temporal correlations in ETa were strongest for distances in time around 12 months (yearly cycle) and less than three months. Spatial correlations were smaller under drought conditions (in the year 2018). Furthermore, combination of multiple ET-LYS from different sites improved the predictability of ET-LYS for another site, suggesting that ET-LYS can be predicted well using ET-LYS from different neighboring sites. Overall, lysimeter measurements can provide information at much larger scales compared to their small measurement area.

中文翻译：

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分析溶度计测量的实际蒸散量的尺度依赖性空间相关性


准确测定实际蒸散量 （ETa） 在水文学、气象学、生态学和农业等各个研究领域都很重要。原位 ETa 可以使用称量溶度计和涡流相关素来确定。然而，尽管被认为是测量 ETa 的最精确的原位方法，但溶度计测量的信息内容仍然知之甚少。在这里，我们检查了用溶度仪 （ET-LYS） 在不同位置测量的 ETa 和通过涡度协方差 （ET-EC） 在不同位置测量的 ETa 之间的空间相关性。这是在 2015 年至 2020 年期间完成的，并使用 23 个溶度计和 4 个涡度相关塔对不同的空间（范围：0 至 500 公里）和时间尺度（范围：1 天至 1 年）进行了分析。我们发现：（a） 在小区尺度上相同的溶出度计显示出 ET-LYS 的极高相关性;（b） 站点之间 ET-LYS 每日标准化异常的 Pearson 相关性表现出中度到高度相关性，并且与 ET-EC 相似，表明溶出仪在 ETa 方面通常与 EC 一样具有代表性，并且可以在景观和更大的区域尺度上提供某些信息。在冬季，ET-LYS 的空间相关性较小;（c） 小波分析表明，ETa 中 12 个月（年周期）左右和不到 3 个月的时间距离的时间相关性最强。在干旱条件下（2018 年），空间相关性较小。此外，来自不同站点的多个 ET-LYS 的组合提高了另一个站点的 ET-LYS 的可预测性，表明使用来自不同相邻站点的 ET-LYS 可以很好地预测 ET-LYS。 总体而言，与较小的测量区域相比，溶度计测量可以在更大的尺度上提供信息。