Abstract. The eddy-covariance method provides the most direct estimates for fluxes between ecosystems and the atmosphere. However, dispersive fluxes can occur in the presence of secondary circulations, which can inherently not be captured by such single-tower measurements. In this study, we present options to correct local flux measurements for such large-scale transport based on a non-local parametric model that has been developed from a set of idealized LES runs for three real-world sites. The test sites DK-Sor, DE-Fen, and DE-Gwg, represent typical conditions in the mid-latitudes with different measurement height, different terrain complexity and different landscape-scale heterogeneity. Different ways to determine the boundary-layer height, which is a necessary input variable for modelling the dispersive fluxes, are applied, either from operational radio-soundings and local in-situ measurements for the flat site or from backscatter-intensity profile obtained from collocated ceilometers for the two sites in complex terrain. The adjusted total fluxes are evaluated by assessing the improvement in energy balance closure and by comparing the resulting latent heat fluxes with evapotranspiration rates from nearby lysimeters. The results show that not only the accuracy of the flux estimates is improved but also the precision, which is indicated by RMSE values that are reduced by approximately 50 %. Nevertheless, it needs to be clear that this method is intended to correct for a bias in eddy-covariance measurements due to the presence of large-scale dispersive fluxes. Other reasons potentially causing a systematic under- or overestimation, such as low-pass filtering effects and missing storage terms, still need to be considered and minimized as much as possible. Moreover, additional transport induced by surface heterogeneities is not considered.

中文翻译：

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使用基于 LES 的方法校正大规模通量的局部湍流通量测量值的选项

摘要。涡旋协方差方法为生态系统和大气之间的通量提供了最直接的估计。然而，在存在二次循环的情况下可能会出现色散通量，而这种单塔测量本身就无法捕获。在这项研究中，我们提出了基于非局部参数模型来校正这种大规模传输的局部通量测量值的选项，该模型是从一组理想化的 LES 运行为三个真实世界站点开发的。试验场DK-Sor、DE-Fen和DE-Gwg代表了中纬度地区不同测量高度、不同地形复杂度和不同景观尺度异质性的典型条件。应用不同的方法来确定边界层高度，边界层高度是模拟色散通量的必要输入变量，要么来自平坦站点的操作无线电探测和本地原位测量，要么来自复杂地形中两个站点的并置云高仪获得的反向散射强度剖面。调整后的总通量是通过评估能量平衡闭合的改进以及通过将产生的潜热通量与附近蒸散仪的蒸散率进行比较来评估的。结果表明，不仅通量估计的准确度得到了提高，而且精度也得到了提高，这由降低约 50% 的 RMSE 值表示。然而，需要明确的是，该方法旨在校正涡度协方差测量中由于存在大规模色散通量而产生的偏差。其他可能导致系统性低估或高估的原因，诸如低通滤波效应和丢失存储项等，仍然需要考虑并尽可能减少。此外，不考虑由表面异质性引起的额外运输。