Estimating uncertainty of the WMO mole fraction scale for carbon dioxide in air
Estimating uncertainty of the WMO mole fraction scale for carbon dioxide in air
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DOI：
10.1029/2005jd006003
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发表时间：
2006-04
影响因子：
--
通讯作者：
C. Zhao;C. Zhao;P. Tans
中科院分区：
文献类型：
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作者：
C. Zhao;C. Zhao;P. Tans
[1]目前的WMO CO2摩尔分数标度包括一套15种空气中CO2的主要标准校准气体，CO2摩尔分数范围为250至520 μmol mol−1。自1995年WMO CO2专家组将维护WMO尺度的责任从斯克里普斯海洋学研究所（SIO）移交给气候监测和诊断实验室（CMDL）以来，WMO的15个基本标准已被校准，首先在SIO，然后每隔1至2年由CMDL压力测量系统进行校准。在绝对意义上，15个一级标准品的不确定度估计为0.069 μmol mol−1（一西格玛）。测压校准结果表明，从1996年到2004年，没有证据表明Primaries的总体漂移。为了延长一级标准品的使用寿命，CMDL总是通过NELLY分析仪将天平转移到二级标准品上。讨论了分析仪随机误差引起的不确定度和参考气体摩尔分数不确定度引起的传播误差。从1979年到现在，NATURAL转移校准的精度约为0.014 μmol mol−1。从理论上计算了不确定度的传播。在插值的情况下，当使用原色作为参考气体时，传播误差估计在0.06和0.07 μmol mol−1之间。CMDL二级标准校准通过NATIONAL分析仪转移到工作标准，工作标准通常用于测量WMO全球大气监视监测计划中的大气CO2摩尔分数。工作标准品的不确定度估计为0.071 μmol mol−1（一西格玛绝对标度）。工作标准品之间的一致性由各水平下向下转移校准的随机误差确定，约为0.02 μmol mol−1。为了与独立的绝对标度进行比较，来自日本筑波国立环境研究所（NIES）的五个重量标准品（CO2摩尔分数范围为350至390 μmol mol−1）相对于CMDL二级标准品进行了校准。NIES重量分析和CMDL分析的CO2摩尔分数之间差异的平均值和标准偏差为0.004 ± 0.03 μmol mol−1。
[1] The current WMO CO2 Mole Fraction Scale consists of a set of 15 CO2-in-air primary standard calibration gases ranging in CO2 mole fraction from 250 to 520 μmol mol−1. Since the WMO CO2 Expert Group transferred responsibility for maintaining the WMO Scale from the Scripps Institution of Oceanography (SIO) to the Climate Monitoring and Diagnostics Laboratory (CMDL) in 1995, the 15 WMO primary standards have been calibrated, first at SIO and then at regular intervals, between 1 and 2 years, by the CMDL manometric system. The uncertainty of the 15 primary standards was estimated to be 0.069 μmol mol−1 (one-sigma) in the absolute sense. Manometric calibrations results indicate that there is no evidence of overall drift of the Primaries from 1996 to 2004. In order to lengthen the useful life of the Primary standards, CMDL has always transferred the scale via NDIR analyzers to the secondary standards. The uncertainties arising from the analyzer random error and the propagation error due to the uncertainty of the reference gas mole fraction are discussed. Precision of NDIR transfer calibrations was about 0.014 μmol mol−1 from 1979 to present. Propagation of the uncertainty was calculated theoretically. In the case of interpolation the propagation error was estimated to be between 0.06 and 0.07 μmol mol−1 when the Primaries were used as the reference gases via NDIR transfer calibrations. The CMDL secondary standard calibrations are transferred via NDIR analyzers to the working standards, which are used routinely for measuring atmospheric CO2 mole fraction in the WMO Global Atmosphere Watch monitoring program. The uncertainty of the working standards was estimated to be 0.071 μmol mol−1 in the one-sigma absolute scale. Consistency among the working standards is determined by the random errors of downward transfer calibrations at each level and is about 0.02 μmol mol−1. For comparison with an independent absolute scale, the five gravimetric standards from the National Institute for the Environmental Studies (NIES) in Tsukuba, Japan, ranging in CO2 mole fraction from 350 to 390 μmol mol−1 have been calibrated relative to the CMDL secondary standards. The average and standard deviation of the differences between the NIES gravimetric and CMDL analyzed CO2 mole fraction are 0.004 ± 0.03 μmol mol−1.