Abstract Surface-atmosphere fluxes are known to vary at multiple time scales, but uncertainty is high as to how fluxes change spatially within regions. With an increase in the number of eddy covariance towers, we are now able to examine the geospatial coherence of ecosystem fluxes, using time-series correlation. Eighteen sites from Michigan and Wisconsin were used in this study, ranging from 100 m to 600 km apart. Surface-atmosphere fluxes from a six-month period were used to quantify spatial coherence on a pair-wise basis. Using geospatial statistics, carbon and sensible heat (H) fluxes were found to be 95% correlated directly outside of their flux footprint and 56% correlated up to a distance of ~35 km. Latent (LE) and momentum (τ) fluxes were less correlated, 83% directly outside of their flux footprint and 40% at a distance of ~130 km albeit, at a much larger spatial distance than for the carbon and sensible heat fluxes. All fluxes showed strong spectral resonance at diel and seasonal timescales, with 1-, 2- and 3-month periods being common modes of variability among H, LE, and τ fluxes. Results based on Empirical Orthogonal Function show distinct transitions of net ecosystem exchange from fall to winter before photosynthesis or respiration while H and τ do not exhibit coherent trends. This work demonstrates the potential of quantifying geospatial coherence of surface-atmosphere fluxes in the Midwestern United States, with the ability to predict fluxes beyond the spatial limit of a single flux tower footprint. Ultimately, expanding the flux measurements to larger scales would allow better spatial scaling of terrestrial surface-atmosphere fluxes between tower footprint and modeling or remote sensing scales.

中文翻译：

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五大湖上游地区地表大气通量的地理空间相干性

摘要 已知地表大气通量在多个时间尺度上变化，但通量如何在区域内空间变化的不确定性很高。随着涡流协方差塔数量的增加，我们现在能够使用时间序列相关性检查生态系统通量的地理空间一致性。本研究使用了密歇根州和威斯康星州的 18 个站点，相距 100 m 到 600 km。六个月期间的地表大气通量被用于在成对的基础上量化空间相干性。使用地理空间统计数据，发现碳和感热 (H) 通量在其通量足迹之外直接相关 95%，在约 35 公里的距离内相关性为 56%。潜在 (LE) 和动量 (τ) 通量的相关性较低，83% 直接在其通量足迹之外，40% 在约 130 公里的距离内，尽管，比碳和显热通量大得多的空间距离。所有通量在日间和季节性时间尺度上都显示出强烈的光谱共振，1、2 和 3 个月是 H、LE 和 τ 通量之间常见的变异模式。基于经验正交函数的结果表明，在光合作用或呼吸作用之前，净生态系统交换从秋季到冬季有明显的转变，而 H 和 τ 没有表现出一致的趋势。这项工作证明了量化美国中西部地表大气通量的地理空间相干性的潜力，能够预测超出单个通量塔足迹空间限制的通量。最终，