Accuracies of field CO2−H2O data from open-path eddy-covariance flux systems: Assessment based on atmospheric physics and biological environment

IF 1.8 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Xinhua Zhou, Tian Gao, Ning Zheng, Yanlei Li, Fengyuan Yu, T. Awada, Jiaojun Zhu
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引用次数: 0

Abstract

Abstract. Ecosystem CO2−H2O data measured vastly from open-path eddy-covariance (OPEC) systems by infrared analyzers have numerous applications in biogeosciences. To assess the applicability, data uncertainties from measurements are needed. The uncertainties are sourced from infrared analyzers in zero drift, gain drift, cross-sensitivity, and precision variability. The sourced uncertainties are individually specified for analyzer performance, but no methodology exists to comprehend these individual uncertainties into a cumulative error for the specification of an overall accuracy, which is ultimately needed. Using the methodology for close-path eddy-covariance systems, this accuracy for OPEC systems is determined from all individual uncertainties via an accuracy model further formulated into CO2 and H2O accuracy equations. Based on atmospheric physics and the biological environment, these equations are used to evaluate CO2 accuracy (±1.21 20 mgCO2 m−3, relatively ±0.19 %) and H2O accuracy (±0.10 gH2O m−3, relatively ±0.18 % in saturated air at 35 °C and 101.325 kPa). Cross-sensitivity and precision variability are minor, although unavoidable, uncertainties. Zero drifts and gain drifts are major uncertainties but are adjustable via corresponding zero and span procedures during field maintenance. The equations provide rationales to assess and guide the procedures. In an atmospheric CO2 background, CO2 zero and span procedures can narrow CO2 accuracy by 40 %, from ±1.21 to ±0.72 mgCO2 m−3. In hot and humid weather, H2O gain drift potentially adds more to H2O measurement uncertainty, which requires more attention. If H2O zero and span procedures can be performed practically from 5 to 35 ºC, the poorest H2O accuracy can be improved by 30 %, from ±0.10 to ±0.07 gH2O m−3. Under freezing conditions, an H2O span is both impractical and unnecessary, but the zero procedure becomes imperative to minimize H2O measurement uncertainty. In cold/dry conditions, the zero procedure for H2O, along with CO2, is an operational and efficient option to ensure and improve H2O accuracy.
开路涡流协方差通量系统现场CO2−H2O数据的准确性:基于大气物理和生物环境的评估
摘要通过红外分析仪从开放路径涡协方差(OPEC)系统中大量测量的生态系统CO2−H2O数据在生物地球科学中有许多应用。为了评估适用性,需要测量数据的不确定性。不确定性来源于红外分析仪的零漂移、增益漂移、交叉灵敏度和精度可变性。来源的不确定性是针对分析仪性能单独指定的,但没有任何方法可以将这些单独的不确定性理解为最终需要的总体精度规范的累积误差。使用近程涡流协方差系统的方法,通过进一步公式化为CO2和H2O精度方程的精度模型,从所有个体不确定性中确定欧佩克系统的精度。基于大气物理学和生物环境,这些方程用于评估CO2精度(±1.21 20 mgCO2 m−3,相对±0.19%)和H2O精度(在35°C和101.325 kPa的饱和空气中,±0.10 gH2O m−3相对±0.18%)。交叉灵敏度和精度的变化是微小的,尽管不可避免的,不确定性。零漂移和增益漂移是主要的不确定性,但在现场维护期间可通过相应的零和量程程序进行调整。这些方程式为评估和指导程序提供了依据。在大气CO2背景下,CO2归零和量程程序可以将CO2准确度缩小40%,从±1.21降至±0.72 mgCO2 m−3。在湿热天气中,H2O增益漂移可能会增加H2O测量的不确定性,这需要更多的关注。如果H2O调零和量距程序实际上可以在5到35ºC之间执行,则最差的H2O精度可以提高30%,从±0.10到±0.07 gH2O m−3。在冻结条件下,H2O量程既不切实际又不必要,但零点程序对于最大限度地减少H2O测量的不确定性变得至关重要。在寒冷/干燥条件下,H2O和CO2的归零程序是一种可操作且有效的选择,可确保和提高H2O的准确性。
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来源期刊
Geoscientific Instrumentation Methods and Data Systems
Geoscientific Instrumentation Methods and Data Systems GEOSCIENCES, MULTIDISCIPLINARYMETEOROLOGY-METEOROLOGY & ATMOSPHERIC SCIENCES
CiteScore
3.70
自引率
0.00%
发文量
23
审稿时长
37 weeks
期刊介绍: Geoscientific Instrumentation, Methods and Data Systems (GI) is an open-access interdisciplinary electronic journal for swift publication of original articles and short communications in the area of geoscientific instruments. It covers three main areas: (i) atmospheric and geospace sciences, (ii) earth science, and (iii) ocean science. A unique feature of the journal is the emphasis on synergy between science and technology that facilitates advances in GI. These advances include but are not limited to the following: concepts, design, and description of instrumentation and data systems; retrieval techniques of scientific products from measurements; calibration and data quality assessment; uncertainty in measurements; newly developed and planned research platforms and community instrumentation capabilities; major national and international field campaigns and observational research programs; new observational strategies to address societal needs in areas such as monitoring climate change and preventing natural disasters; networking of instruments for enhancing high temporal and spatial resolution of observations. GI has an innovative two-stage publication process involving the scientific discussion forum Geoscientific Instrumentation, Methods and Data Systems Discussions (GID), which has been designed to do the following: foster scientific discussion; maximize the effectiveness and transparency of scientific quality assurance; enable rapid publication; make scientific publications freely accessible.
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