Abstract. The NOAA Global Monitoring Laboratory serves as the WMO/GAW Central Calibration Laboratory (CCL) for CO₂ and is responsible for maintaining the WMO/GAW mole fraction scale used as a reference within the WMO/GAW program. The current WMO-CO₂-X2007 scale is embodied by 15 aluminum cylinders containing natural air, with CO₂ mole fractions determined using the NOAA manometer from 1995 to 2006. We have made two minor corrections to historical manometric records: fixing an error in the applied second virial coefficient of CO₂, and accounting for loss of a small amount of CO₂ to materials in the manometer during the measurement process. By incorporating these corrections, extending the measurement records of the original 15 primary standards through 2015, and adding four new primary standards to the suite, we define a new scale, identified as WMO-CO₂-X2019. The new scale is 0.18 μmol mol⁻¹ (ppm) greater than the previous scale at 400 ppm CO₂. While this difference is small in relative terms (0.045 %), it is significant in terms of atmospheric monitoring. All measurements of tertiary-level standards will be reprocessed to WMO-CO₂-X2019. The new scale is more internally consistent than WMO-CO₂-X2007 owing to revisions in propagation, and should result in an overall improvement in atmospheric data records traceable to the CCL.

中文翻译：

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修订WMO / GAW CO ₂校准秤

摘要。NOAA全球监测实验室充当WMO / GAW CO ₂中央校准实验室（CCL），并负责维护WMO / GAW摩尔分数比例，作为WMO / GAW计划中的参考。当前的WMO-CO ₂ -X2007秤由包含自然空气的15个铝制圆柱体组成，其中1995年至2006年使用NOAA压力计确定了CO ₂摩尔分数。我们对历史的压力记录进行了两个小修正：修正了应用第二CO ₂维里系数，并考虑到少量CO _2的损失在测量过程中对压力计中的材料的影响。通过合并这些更正，将原始15个主要标准的测量记录扩展到2015年，并在套件中添加四个新的主要标准，我们定义了一个新的标度，标识为WMO-CO ₂ -X2019。新比例为400 ppm CO _2时比以前的比例大0.18μmolmol ^-1（ppm）。尽管此差异相对而言很小（0.045％），但在大气监测方面却很重要。所有第三级标准的测量结果都将重新处理为WMO-CO ₂ -X2019。新比例比WMO-CO _2在内部更具一致性-X2007由于传播方面的修订，应导致可追溯到CCL的大气数据记录的全面改善。