Routine uncertainty propagation for the marine carbon dioxide system
Routine uncertainty propagation for the marine carbon dioxide system
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DOI：
10.1016/j.marchem.2018.10.006
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发表时间：
2018-11-20
期刊：
影响因子：
3
通讯作者：
Gattuso, Jean-Pierre
中科院分区：
文献类型：
--
作者：
Orr, James C.;Epitalon, Jean-Marie;Gattuso, Jean-Pierre
成对的海洋碳酸盐系统变量通常用于计算其他变量，但很少报告这些结果以及不确定性的估计。尽管传播这些不确定性的程序是众所周知的，但它尚未在计算海洋碳酸盐化学的公共软件包中提供，而公共软件包是社区所依赖的基本工具。为了弥补这一缺点，对其中的四个包进行了扩展，以计算计算变量相对于每个输入变量的敏感性，并使用这些敏感性以及用户指定的输入不确定性估计（标准不确定性）来传播计算变量的不确定性（组合标准不确定性）。这些软件包的灵敏度彼此一致，并且与分析解决方案的灵敏度一致，误差在 0.01% 以内；对于组合标准不确定度，软件包之间也存在类似的一致性。一个包用于量化计算变量、海水条件和用作输入的选定的一对碳酸盐系统变量之间传播的不确定性如何变化。使用新型图表探讨了输入测量值对和各种其他输入数据（平衡常数等）的标准不确定性对传播不确定性的相对贡献。这些误差空间图表明，超出当今最先进的输入对测量不确定度的进一步改进通常对于降低组合标准不确定度是无效的，因为常数的贡献更大。同样，使用输入对的更加不确定的测量并不总是显着恶化组合标准不确定性。正如预期的那样，对组合标准不确定度影响最大的常数通常是 K-1 和 K-2。然而文石和方解石的计算饱和状态的传播不确定性更多来自于它们的溶解度积。因此，饱和状态的相对组合标准不确定度百分比大于碳酸根离子浓度。这些不确定性的常规传播应该成为标准做法。
Pairs of marine carbonate system variables are often used to calculate others, but those results are seldom reported with estimates of uncertainties. Although the procedure to propagate these uncertainties is well known, it has not been offered in public packages that compute marine carbonate chemistry, fundamental tools that are relied on by the community. To remedy this shortcoming, four of these packages were expanded to calculate sensitivities of computed variables with respect to each input variable and to use those sensitivities along with user-specified estimates of input uncertainties (standard uncertainties) to propagate uncertainties of calculated variables (combined standard uncertainties). Sensitivities from these packages agree with one another and with analytical solutions to within 0.01%; similar agreement among packages was found for the combined standard uncertainties. One package was used to quantify how propagated uncertainties vary among computed variables, seawater conditions, and the chosen pair of carbonate system variables that is used as input. The relative contributions to propagated uncertainties from the standard uncertainties of the input pair of measurements and various other input data (equilibrium constants etc) were explored with a new type of diagram. These error-space diagrams illustrate that further improvement beyond today's state-of-the-art measurement uncertainties for the input pair would generally be ineffective at reducing the combined standard uncertainties because the contribution from the constants is larger. Likewise, using much more uncertain measurements of the input pair does not always substantially worsen combined standard uncertainty. The constants that contribute most to combined standard uncertainties are generally K-1 and K-2, as expected. Yet more of the propagated uncertainty in the computed saturation states of aragonite and calcite comes from their solubility products. Thus percent relative combined standard uncertainties for the saturation states are larger than for the carbonate ion concentration. Routine propagation of these uncertainties should become standard practice.