In the first half of the twentieth century the measurement of rates of exchange of momentum, heat, and especially water between the terrestrial surface and the atmosphere was an elusive challenge. A wide variety of methods evolved, ranging from reliance on drag plates, evaporation pans, and weighed lysimeters to a variety of methods based on measurement of vertical gradients in the air. None of these provided great confidence in the results. The promise of direct measurement by eddy covariance was held at bay by the lack of suitable fast-response instrumentation and the analytical requirement to average the products of pairs of these fast-response signals. Developments starting in the 1950s have now largely solved the problems that previously limited eddy covariance. Here, the history of flux measurement is summarized, and the path to now-standard capabilities is explored. The currently active major international programs making use of the modern instrumentation are addressed (with the focus on CO 2 and CH 4 , as befitting global concerns regarding climate change), with particular attention to the emerging need to revisit the fetch and footprint constraints that confronted early workers. Finally, some areas of continuing uncertainty are mentioned, with an implicit request for increased experimental attention.

中文翻译：

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陆上通量的测量：能力、起源和剩余挑战

在 20 世纪上半叶，测量地球表面和大气之间的动量、热量，尤其是水的交换率是一项难以捉摸的挑战。各种各样的方法得到了发展，从依赖拖板、蒸发盘和称重蒸渗仪到基于空气垂直梯度测量的各种方法。这些都没有为结果提供很大的信心。由于缺乏合适的快速响应仪器以及对这些快速响应信号对的乘积求平均的分析要求，涡流协方差直接测量的前景受到阻碍。1950 年代开始的发展现在在很大程度上解决了以前限制涡流协方差的问题。在这里，总结了通量测量的历史，并且探索了通向现在标准功能的路径。目前正在开展的使用现代仪器的主要国际计划得到解决（重点关注 CO 2 和 CH 4 ，因为它们适合全球对气候变化的关注），特别关注重新审视所面临的获取和足迹限制的新需求早期工人。最后，还提到了一些具有持续不确定性的领域，并隐含地要求增加实验注意力。