Abstract Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring upscaling and field measurements such as eddy covariance measuring only the evapotranspiration. During the summer of 2014 an eddy covariance device was used to measure the evapotranspiration of a growing maize field at the HOAL catchment. The stable isotope technique and a Lagrangian near field theory (LNF) were then utilized to partition the evapotranspiration into evaporation and transpiration, using the concentration and isotopic ratio of water vapour within the canopy. The stable isotope estimates of the daily averages of the fraction of evapotranspiration (Ft) ranged from 43.0–88.5%, with an average value of 67.5%, while with the LNF method, Ft was found to range from 52.3–91.5% with an average value of 73.5%. Two different parameterizations for the turbulent statistics were used, with both giving similar R2 values, 0.65 and 0.63 for the Raupach and Leuning parameterizations, with the Raupach version performing slightly better. The stable isotope method demonstrated itself to be a more robust method, returning larger amounts of useable data, however this is limited by the requirement of much more additional data.

中文翻译：

---

在小型农业集水区使用稳定同位素和拉格朗日色散分析划分蒸散

摘要 由于环境的异质性，在田间尺度上测量蒸发和蒸腾是复杂的，点测量需要放大，而场测量（如涡度协方差仅测量蒸发蒸腾）。2014 年夏天，使用涡流协方差装置测量 HOAL 集水区正在生长的玉米田的蒸散量。然后利用稳定同位素技术和拉格朗日近场理论 (LNF)，利用冠层内水蒸气的浓度和同位素比将蒸发蒸腾分为蒸发和蒸腾。蒸发蒸腾部分 (Ft) 的日平均值的稳定同位素估计值范围为 43.0-88.5%，平均值为 67.5%，而使用 LNF 方法，发现 Ft 的范围为 52.3-91。5%，平均值为 73.5%。湍流统计使用了两种不同的参数化，两者都给出了相似的 R2 值，Raupach 和 Leuning 参数化的 R2 值分别为 0.65 和 0.63，Raupach 版本的性能稍好一些。稳定同位素方法证明自己是一种更可靠的方法，返回大量可用数据，但是这受到需要更多额外数据的限制。