Deriving stratospheric age of air spectra using an idealized set of chemically active trace gases
Deriving stratospheric age of air spectra using an idealized set of chemically active trace gases
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DOI：
10.5194/acp-19-5269-2019
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发表时间：
2019-04
影响因子：
6.3
通讯作者：
M. Hauck;Frauke Fritsch;H. Garny;A. Engel
中科院分区：
文献类型：
--
作者：
M. Hauck;Frauke Fritsch;H. Garny;A. Engel
抽象的。从观测角度分析平流层迁移，往往是通过评价长寿命微量气体的空气平均年龄值来实现的。然而，这提供了更多的了解一般的运输强度，而不是其机制。导出完整的渡越时间分布（年龄谱）是可取的，但他们的直接测量推导是困难的。迄今为止，它主要基于模型工作。本文介绍了一种改进的由短寿命痕量气体混合比反演年龄谱的方法，并在理想模式模拟中研究了其基本原理。为了充分描述运输季节性，该方法包括施加的季节性周期以获得多峰谱。一个ECHAM/MESSy大气化学（EMAC）模型模拟的方法的概念的一般证明和功能的40个放射性示踪气体与不同的化学寿命，以及40个化学惰性脉冲示踪气体的理想化数据集计算脉冲年龄谱。它评估是否修改后的逆方法结合季节性周期可以提供匹配的年龄谱时，化学是众所周知的。年度和季节平均逆谱脉冲谱，包括第一和第二时刻，以及它们之间的比率，以评估这些时间尺度上的性能进行比较。结果表明，修正的逆年龄谱在全球范围内与年和季节脉冲年龄谱的匹配性很好，超过了1.5年的平均空气年龄。强加的季节性周期出现作为一个可靠的工具，包括运输季节性的年龄谱。低于1.5年的平均年龄的空气，对流层的影响加剧，并打破了假设的单一入口通过热带对流层顶，导致不准确的光谱，特别是在北方半球。强加的季节性周期错误地规定在这个较低的区域的季节性条目，并没有导致更好的协议之间的逆和脉冲年龄谱没有进一步的改进。侧重于未来应用的观测数据的测试意味着，具有5至10个物种的痕量气体的子集是足够的推导出匹配良好的年龄谱。这些子集还可以补偿化学寿命知识中高达± 20%的平均不确定性，如果所得到的光谱的模态年龄和振幅的偏差约为± 10%的话。
Abstract. Analysis of stratospheric transport from an observational point of view is frequently realized by evaluation of the mean age of air values from long-lived trace gases. However, this provides more insight into general transport strength and less into its mechanism. Deriving complete transit time distributions (age spectra) is desirable, but their deduction from direct measurements is difficult. It is so far primarily based on model work. This paper introduces a modified version of an inverse method to infer age spectra from mixing ratios of short-lived trace gases and investigates its basic principle in an idealized model simulation. For a full description of transport seasonality the method includes an imposed seasonal cycle to gain multimodal spectra. An ECHAM/MESSy Atmospheric Chemistry (EMAC) model simulation is utilized for a general proof of concept of the method and features an idealized dataset of 40 radioactive trace gases with different chemical lifetimes as well as 40 chemically inert pulsed trace gases to calculate pulse age spectra. It is assessed whether the modified inverse method in combination with the seasonal cycle can provide matching age spectra when chemistry is well-known. Annual and seasonal mean inverse spectra are compared to pulse spectra including first and second moments as well as the ratio between them to assess the performance on these timescales. Results indicate that the modified inverse age spectra match the annual and seasonal pulse age spectra well on global scale beyond 1.5 years of mean age of air. The imposed seasonal cycle emerges as a reliable tool to include transport seasonality in the age spectra. Below 1.5 years of mean age of air, tropospheric influence intensifies and breaks the assumption of single entry through the tropical tropopause, leading to inaccurate spectra, in particular in the Northern Hemisphere. The imposed seasonal cycle wrongly prescribes seasonal entry in this lower region and does not lead to a better agreement between inverse and pulse age spectra without further improvement. Tests with a focus on future application to observational data imply that subsets of trace gases with 5 to 10 species are sufficient for deriving well-matching age spectra. These subsets can also compensate for an average uncertainty of up to ±20 % in the knowledge of chemical lifetime if a deviation of circa ±10 % in modal age and amplitude of the resulting spectra is tolerated.