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首页> 外文期刊>Agricultural and Forest Meteorology >Effects of different eddy covariance correction schemes on energy balance closure and comparisons with the modified Bowen ratio system
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Effects of different eddy covariance correction schemes on energy balance closure and comparisons with the modified Bowen ratio system

机译：不同涡度协方差校正方案对能量平衡闭合的影响以及与改进的Bowen比率系统的比较

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Eddy covariance (EC) and modified Bowen ratio (MBR) systems have been shown to yield subtly different estimates of sensible heat (H), latent heat (LE), and CO fluxes (Fc). Our study analyzed the discrepancies between these two systems by first considering the role of the data processing algorithm used to estimate fluxes using EC and later examining the effects of atmospheric stability on discrepancies between EC and MBR. We found that EC correction algorithms disproportionately increase the magnitude of LE and Fc, and consequently have a strong effect on the Bowen ratio measured by EC. Two corrections not universally employed were each found to account for up to 20% of LE and Fc: the correction for signal asynchrony by adjusting the lag between the IRGA and the sonic anemometer, and the frequency domain correction for path-length averaging in both instruments. Comparison of fluxes between two EC systems 10m apart showed that LE and Fc are inherently more variable than H, highlighting the role of field heterogeneity in determining canopy gas exchange at very small spatial scales. When all relevant corrections were applied, there was no bias for H and LE between EC and MBR. An examination of discrepancies between EC and MBR showed that the discrepancies were highest during neutral periods when shear drove vertical mixing much more than buoyancy. During these neutral periods, the correlation between T, HO, and CO was much lower on average, which violates the similarity assumption exploited in the MBR technique. The largest discrepancies in Fc in both systems were clearly visible when plotted against a light-response curve, which creates the possibility of using a screening technique to exclude data that depart markedly from other recently collected data. The EC system tended to have the largest departures from the expected value at low light and during the night, while the MBR system tended to show occasionally spikes of high photosynthetic uptake.
机译：涡度协方差（EC）和修正的Bowen比（MBR）系统已显示出对显热（H），潜热（LE）和一氧化碳通量（Fc）的不同估算。我们的研究分析了这两个系统之间的差异，首先考虑了使用EC估计通量的数据处理算法的作用，然后研究了大气稳定性对EC和MBR之间差异的影响。我们发现，EC校正算法会不成比例地增加LE和Fc的大小，因此对EC测得的Bowen比有很强的影响。发现两种未普遍采用的校正方法分别占LE和Fc的20％：通过调整IRGA和声波风速计之间的延迟来进行信号异步校正，以及在两种仪器中均通过路径长度平均进行频域校正。比较两个相距10m的EC系统之间的通量，发现LE和Fc本质上比H更具可变性，突出了场异质性在确定很小空间尺度上的冠层气体交换中的作用。应用所有相关的更正后，EC和MBR之间的H和LE没有偏差。对EC和MBR之间的差异进行检查后发现，在中性时期，当剪切力推动垂直混合作用远大于浮力作用时，差异最大。在这些中性期间，T，HO和CO之间的相关性平均较低，这违背了MBR技术中采用的相似性假设。当对照光响应曲线作图时，两个系统中Fc的最大差异清晰可见，这提供了使用筛选技术排除明显偏离其他最近收集的数据的可能性。在弱光和夜间，EC系统趋向于与期望值的最大偏离，而MBR系统趋于偶尔显示出高光合吸收的峰值。

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