We use 148 airborne vertical profiles of CO₂ for frontal cases from the summer 2016 Atmospheric Carbon and Transport—America (ACT‐America) campaign to evaluate the skill of 10 global CO₂ in situ inversion models from the version 7 Orbiting Carbon Observatory–2 (OCO‐2) Model Intercomparison Project (MIP). Model errors (model posterior—observed CO₂ dry air mole fractions) were categorized by region (Mid‐Atlantic, Midwest, and South), frontal sector (warm or cold), and transport model (predominantly Tracer Model 5 (TM5) and Goddard Earth Observing System—Chemistry [GEOS‐Chem]). All inversions assimilated the same CO₂ observations. Overall, the median inversion profiles reproduce the general structures of the observations (enhanced/depleted low‐level CO₂ in warm/cold sectors), but 1) they underestimate the magnitude of the warm/cold sector mole fraction difference, and 2) the spread among individual inversions can be quite large (>5 ppm). Uniquely in the Mid‐Atlantic, inversion biases segregated according to atmospheric transport model, where TM5 inversions biases were −3 to −4 ppm in warm sectors, while those of GEOS‐Chem were +2 to +3 ppm in cold sectors. The large spread among the mean posterior CO₂ profiles is not explained by the different atmospheric transport models. These results show that the inversion systems themselves are the dominant cause of this spread, and that the aircraft campaign data are clearly able to identify these large biases. Future controlled experiments should identify which inversions best reproduce mid‐latitude CO₂ mole fractions, and how inversion system components are linked to system performance.

中文翻译：

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使用ACT-America项目的飞机数据对全球CO2反演模型进行区域规模，部门特定评估

我们使用2016年夏季“大气碳与运输-美国”（ACT-America）活动的148个机载CO ₂垂直剖面的正面情况，来评估版本7轨道碳观测站–2的10个全球CO ₂原位反演模型的技能。（OCO-2）模型比较项目（MIP）。模型错误（模型后观察到的CO ₂干空气摩尔分数）按地区（中大西洋，中西部和南部），额部（温暖或寒冷）和运输模型（主要是Tracer Model 5（TM5）和Goddard）分类。地球观测系统-化学[GEOS-Chem]）。所有反演吸收相同的CO ₂观察。总体而言，中值反演剖面再现了观测的一般结构（暖/冷部门中增强/耗尽的低水平CO ₂），但1）它们低估了暖/冷部门摩尔分数差异的幅度，以及2）各个反演之间的差异可能很大（> 5 ppm）。在大西洋中部，独特的反演偏差是根据大气传输模型来分离的，其中，TM5的反演偏差在温暖的区域为−3至−4 ppm，而GEOS-Chem在寒冷的区域为+2至+3 ppm。平均后验CO _2的分布较大不同的大气传输模型无法解释剖面。这些结果表明，反演系统本身是造成这种扩散的主要原因，而且飞机战役数据显然能够识别出这些大偏差。未来的受控实验应确定哪些反转最能再现中纬度CO ₂摩尔分数，以及反转系统组件如何与系统性能联系起来。