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Possible implications of enhanced chlorofluorocarbon-11 concentrations on ozone

机译：增强氯氟烃-11浓度对臭氧的可能影响

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This numerical model study is motivated by the observed global deviation from assumed emissions of chlorofluorocarbon-11 (CFC-11, CFCl3) in recent years. Montzka et al.?(2018) discussed a strong deviation of the assumed emissions of CFC-11 over the past 15?years, which indicates a violation of the Montreal Protocol for the protection of the ozone layer. An investigation is performed which is based on chemistry–climate model (CCM) simulations that analyze the consequences of an enhanced CFC-11 surface mixing ratio. In comparison to a reference simulation (REF-C2), where a decrease of the CFC-11 surface mixing ratio of about 50 % is assumed from the early 2000s to the middle of the century (i.e., a mixing ratio in full compliance with the Montreal Protocol agreement), two sensitivity simulations are carried out. In the first simulation the CFC-11 surface mixing ratio is kept constant after the year 2002 until 2050 (SEN-C2-fCFC11_2050); this allows a qualitative estimate of possible consequences of a high-level stable CFC-11 surface mixing ratio on the ozone layer. In the second sensitivity simulation, which is branched off from the first sensitivity simulation, it is assumed that the Montreal Protocol is fully implemented again starting in the year 2020, which leads to a delayed decrease of CFC-11 in this simulation (SEN-C2-fCFC11_2020) compared with the reference simulation; this enables a rough and most likely upper-limit assessment of how much the unexpected CFC-11 emissions to date have already affected ozone. In all three simulations, the climate evolves under the same greenhouse gas scenario (i.e., RCP6.0) and all other ozone-depleting substances decline (according to this scenario). Differences between the reference (REF-C2) and the two sensitivity simulations (SEN-C2-fCFC11_2050 and SEN-C2-fCFC11_2020) are discussed. In the SEN-C2-fCFC11_2050 simulation, the total column ozone (TCO) in the 2040s (i.e., the years 2041–2050) is particularly affected in both polar regions in winter and spring. Maximum discrepancies in the TCO values are identified with reduced ozone values of up to around 30 Dobson units in the Southern Hemisphere (SH) polar region during SH spring (in the order of 15 %). An analysis of the respective partial column ozone (PCO) for the stratosphere indicates that the strongest ozone changes are calculated for the polar lower stratosphere, where they are mainly driven by the enhanced stratospheric chlorine content and associated heterogeneous chemical processes. Furthermore, it was found that the calculated ozone changes, especially in the upper stratosphere, are surprisingly small. For the first time in such a scenario, we perform a complete ozone budget analysis regarding the production and loss cycles. In the upper stratosphere, the budget analysis shows that the additional ozone depletion due to the catalysis by reactive chlorine is partly compensated for by other processes related to enhanced ozone production or reduced ozone loss, for instance from nitrous oxide (NOx). Based on the analysis of the SEN-C2-fCFC11_2020 simulation, it was found that no major ozone changes can be expected after the year 2050, and that these changes are related to the enhanced CFC-11 emissions in recent years.
机译：该数值模型研究由近年来观察到的全球偏离氯氟烃-11（CFC-11，CFCL3）的全局偏差。 Montzka等人。（2018年）（2018年）讨论了过去15年的CFC-11的假定排放的强烈偏离，这表明违反了蒙特利尔议定书来保护臭氧层。进行研究，该研究是基于化学气候模型（CCM）模拟，其分析增强的CFC-11表面混合比的后果。与参考仿真（REF-C2）相比，从2000年代初到世纪初假设CFC-11表面混合比约50％的降低（即，与最完全符合的混合比例蒙特利尔协议协议），进行了两个灵敏度模拟。在第一次模拟中，CFC-11表面混合比在2002年之后保持恒定，直到2050年（SEN-C2-FCFC11_2050）;这允许定性估计对臭氧层对高电平稳定CFC-11表面混合比的可能后果。在从第一灵敏度模拟中分支的第二敏感性模拟中，假设在2020年开始，蒙特利尔协议再次开始再次实现，这导致该模拟中CFC-11的延迟减少（SEN-C2 -fcfc11_2020）与参考仿真相比;这使得迄今为止迄今为止的意外的CFC-11排放量的粗略和最有可能的上限评估已经存在臭氧。在所有三种模拟中，气候在相同的温室气体场景（即RCP6.0）下进化，所有其他臭氧消耗物质下降（根据这一情况）。讨论了参考（参考C2）与两个灵敏度模拟之间的差异（SEN-C2-FCFC11_2050和SEN-C2-FCFC11_2020）。在SEN-C2-FCFC11_2050模拟中，2040年代（即，2041-2050）中的总列臭氧（TCO）在冬季和弹簧中的两个极地区域中特别受到影响。 TCO值中的最大差异在SH弹簧期间（SH）极性区域的南半球（SH）极性区域中的最大臭氧值减少到大约30多个电脑单位（大约15％）。对平流层的各自柱臭氧（PCO）的分析表明，对于极性下划线来计算最强的臭氧变化，在那里它们主要由增强的平坦氯含量和相关的异质化学过程驱动。此外，发现计算出的臭氧变化，特别是在上层层，令人惊讶的是。在这种情况下，我们第一次对生产和丢失周期进行完整的臭氧预算分析。在上层层中，预算分析表明，由反应氯催化引起的另外的臭氧耗竭由与增强的臭氧产生或减少臭氧损失有关的其他方法，例如从氧化亚氮（NOx）。基于SEN-C2-FCFC11_2020模拟的分析，发现在2050年之后可以预期主要臭氧的变化，并且这些变化近年来与增强的CFC-11排放有关。

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