New approach to evaluate satellite-derived XCO2 over oceans by integrating ship and aircraft observations
New approach to evaluate satellite-derived XCO2 over oceans by integrating ship and aircraft observations
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DOI：
10.5194/acp-21-8255-2021
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发表时间：
2021-05
影响因子：
6.3
通讯作者：
Astrid Müller;H. Tanimoto;T. Sugita;T. Machida;S. Nakaoka;P. Patra;J. Laughner;D. Crisp
中科院分区：
文献类型：
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作者：
Astrid Müller;H. Tanimoto;T. Sugita;T. Machida;S. Nakaoka;P. Patra;J. Laughner;D. Crisp
抽象的。卫星观测对地球表面上二氧化碳(XCO2)的柱平均混合比提供了空间分辨率的全球估计。这些数据集的准确性可以在一些地区对照可靠的标准进行验证，但其他地区仍然无法进入。迄今为止，海洋上有限的参考数据阻碍了成功的不确定性量化或偏差纠正工作，并排除了关于某些区域碳循环变化的可靠结论。在这里，我们提出了一种新的方法来分析和评估海洋上XCO2的季节、年际和纬度变化，方法是结合货船(机遇号-SOOP)和商用飞机(客机-轨道痕量气体综合观测网络)的观测，并借助最新的大气化学输送模式计算。“基于观测的列平均二氧化碳”数据集(OBS)的一致性。分析了2014至2017年间西太平洋的卫星估计数据(XCO2)，并评估了其作为参考数据集的效用。我们的结果表明，新的数据集准确地捕捉到了CO2的季节和年际变化。从GOSAT(温室气体观测卫星：国家环境研究所-NIES v02.75；空间大气二氧化碳观测-ACOS v7.3)和OCO-2(轨道碳观测站，v9r)观测对海洋上空的XCO2进行的反演显示，北中纬度地区的负偏差约为百万分之一(Ppm)，这归因于卫星观测的测量不确定性。NIES检索与OBS有较高的一致性。在中纬度地区的XCO2与其他反演法相比较。在低纬地区，它显示的有效数据要少得多，而且散布得很高，因此ACOS和OCO-2似乎更好地代表了碳循环。在不同的时间，所有三次反演的季节周期相对于基于观测的数据显示出1个月的正相移。研究表明，即使这些反演是相辅相成的，仍然存在的不确定性限制了对CO2通量时空变化的准确解释。基于新方法的具有宽纬度覆盖范围的连续长期XCO2数据集具有作为XCO2稳健参考数据集的巨大潜力，并有助于利用卫星观测更好地了解碳循环随气候变化的变化。
Abstract. Satellite observations provide spatially resolved global estimates of column-averaged mixing ratios of CO 2 (XCO 2 ) over the Earth's surface. The accuracy of these datasets can be validated against reliable standards in some areas, but other areas remain inaccessible. To date, limited reference data over oceans hinder successful uncertainty quantification or bias correction efforts and preclude reliable conclusions about changes in the carbon cycle in some regions. Here, we propose a new approach to analyze and evaluate seasonal, interannual, and latitudinal variations of XCO 2 over oceans by integrating cargo-ship (Ship Of Opportunity – SOOP) and commercial aircraft (Comprehensive Observation Network for Trace gases by Airliner – CONTRAIL) observations with the aid of state-of-the art atmospheric chemistry-transport model calculations. The consistency of the “observation-based column-averaged CO 2 ” dataset (obs. XCO 2 ) with satellite estimates was analyzed over the western Pacific between 2014 and 2017, and its utility as a reference dataset evaluated. Our results demonstrate that the new dataset accurately captures seasonal and interannual variations of CO 2 . Retrievals of XCO 2 over the ocean from GOSAT (Greenhouse Gases Observing Satellite: National Institute for Environmental Studies – NIES v02.75; Atmospheric CO 2 Observation from Space – ACOS v7.3) and OCO-2 (Orbiting Carbon Observatory, v9r) observations show a negative bias of about 1 part per million (ppm) in northern midlatitudes, which was attributed to measurement uncertainties of the satellite observations. The NIES retrieval had higher consistency with obs. XCO 2 at midlatitudes as compared to the other retrievals. At low latitudes, it shows many fewer valid data and high scatter, such that ACOS and OCO-2 appear to provide a better representation of the carbon cycle. At different times, the seasonal cycles of all three retrievals show positive phase shifts of 1 month relative to the observation-based data. The study indicates that even if the retrievals complement each other, remaining uncertainties limit the accurate interpretation of spatiotemporal changes in CO 2 fluxes. A continuous long-term XCO 2 dataset with wide latitudinal coverage based on the new approach has great potential as a robust reference dataset for XCO 2 and can help to better understand changes in the carbon cycle in response to climate change using satellite observations.