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Uncertainties in Turbulent Statistics and Fluxes of CO2 Associated With Density Effect Corrections
Geophysical Research Letters ( IF 4.6 ) Pub Date : 2020-07-23 , DOI: 10.1029/2020gl088859
Zhongming Gao 1 , Heping Liu 1 , Evan Arntzen 2 , Douglas P. Mcfarland 2 , Xingyuan Chen 2 , Maoyi Huang 2
Affiliation  

Density effect corrections (DECs) are applied to adjust raw CO2 fluxes measured by eddy covariance (EC) systems with open‐path gas analyzers. DEC is also required for adjusting the measured CO2 concentration fluctuations to obtain the adjusted CO2 concentrations for analyzing turbulent statistics or quantifying fluxes. However, our data show that the power spectra of the DEC‐adjusted CO2 concentrations are distorted in the high‐frequency range, as compared with the corresponding spectra of temperature and water vapor density. This contradicts the similarity behavior of scalars, as suggested by Monin‐Obukhov similarity theory. It is demonstrated that such a distortion is caused by the DEC‐induced spikes in the DEC‐adjusted CO2, altering turbulent statistics of CO2 and scalar similarity between CO2 and other scalars. Our results suggest that CO2 fluxes are overestimated by applying DEC especially under high Bowen ratio conditions, potentially leading to substantial uncertainties in long‐term ecosystem carbon exchange in dry regions.

中文翻译:

与密度效应校正相关的湍流统计和CO2通量的不确定性

密度效应校正(DECs)用于调整由具有开放路径气体分析仪的涡流协方差(EC)系统测量的原始CO 2通量。还需要DEC来调整测量的CO 2浓度波动,以获得调整后的CO 2浓度,以分析湍流统计数据或量化通量。但是,我们的数据表明,与相应的温度和水蒸气密度谱相比,经DEC调整的CO 2浓度的功率谱在高频范围内会失真。正如Monin-Obukhov相似性理论所建议的,这与标量的相似性行为相矛盾。事实证明,这种失真是由DEC调整后的CO中DEC引起的尖峰引起的。参照图2,改变CO 2的湍流统计和CO 2与其他标量之间的标量相似性。我们的结果表明,尤其是在高Bowen比条件下,通过应用DEC高估了CO 2通量,这可能导致干旱地区长期生态系统碳交换存在大量不确定性。
更新日期:2020-08-03
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