Why is Lower Stratospheric Ozone Not Recovering?

为什么平流层低层臭氧没有恢复？

• 批准号: NE/V011863/1
• 负责人: Martyn Chipperfield
• 金额: $ 82.73万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV011863%2F1
• 关键词: Why; Lower; Stratospheric; Ozone; Recovering

Depletion of stratospheric ozone allows larger doses of harmful solar ultraviolet (UV) radiation to reach the surface leading to increases in skin cancer and cataracts in humans and other impacts, such as crop damage. Ozone also affects the Earth's radiation balance and, in particular, ozone depletion in the lower stratosphere (LS) exerts an important climate forcing. While most long-lived ozone-depleting substances (ODSs, e.g. chlorofluorocarbons, CFCs) are now controlled by the United Nations Montreal Protocol and their abundances are slowly declining, there remains significant uncertainty surrounding the rate of ozone layer recovery. Although signs of recovery have been detected in the upper stratosphere and the Antarctic, this is not the case for the lower stratosphere at middle and low latitudes. In fact, contrary to expectations, ozone in this extrapolar lower stratosphere has continued to decrease (by up to 5% since 1998). The reason(s) for this are not known, but suggested causes include changes in atmospheric dynamics or the increasing abundance of short-lived reactive iodine and chlorine species. We will investigate the causes of this ongoing depletion using comprehensive modelling studies and new targeted observations of the short-lived chlorine substances in the lower stratosphere.While the Montreal Protocol has controlled the production of long-lived ODSs, this is not the case for halogenated very short-lived substances (VSLS, lifetimes <6 months), based on the belief that they would not be abundant or persistent enough to have an impact. Recent observations suggest otherwise, with notable increases in the atmospheric abundance of several gases (CH2Cl2, CHCl3), due largely to growth in emissions from Asia. A major US aircraft campaign based in Japan in summer 2021 will provide important new information on how these emissions of short-lived species reach the stratosphere via the Asian Summer Monsoon (ASM). UEA will supplement the ACCLIP campaign by making targeted surface observations in Taiwan and Malaysia which will help to constrain chlorine emissions.The observations will be combined with detailed and comprehensive 3-D modelling studies at Leeds and Lancaster, who have world-leading expertise and tools for the study of atmospheric chlorine and iodine. The modelling will use an off-line chemical transport model (CTM), ideal for interpreting observations, and a coupled chemistry-climate model (CCM) which is needed to study chemical-dynamical feedbacks and for future projections. Novel observations on how gases are affected by gravitational separation will be used to test the modelled descriptions of variations in atmospheric circulation. The CTM will also be used in an 'inverse' mode to trace back the observations of anthropogenic VSLS to their geographical source regions. The models will be used to quantify the flux of short-lived chlorine and iodine species to the stratosphere and to determine their impact on lower stratospheric ozone trends. The impact of dynamical variability will be quantified using the CTM and the drivers of this determined using the CCM. The model results will be analysed using the same statistical models used to derive the decreasing trend in ozone from observations, including the Dynamical Linear Model (DLM). Overall, the results of the model experiments will be synthesised into an understanding of the ongoing decrease in lower stratospheric ozone. This information will then be used to make improved future projections of how ozone will evolve, which will feed through to the policy-making process (Montreal Protocol) with the collaboration of expert partners. The results of the project will provide important information for future international assessments e.g. WMO/UNEP and IPCC reports.

平流层臭氧的消耗使得更大剂量的有害太阳紫外线（UV）辐射到达地表，导致人类皮肤癌和白内障的增加以及其他影响，例如农作物受损。臭氧还影响地球的辐射平衡，特别是平流层低层（LS）的臭氧消耗会产生重要的气候强迫。虽然大多数长寿命臭氧消耗物质（ODS，例如氯氟烃、CFC）现在受到联合国《蒙特利尔议定书》的控制，并且其含量正在缓慢下降，但臭氧层恢复速度仍然存在很大的不确定性。尽管在平流层上层和南极地区已经发现了恢复的迹象，但中低纬度平流层下层的情况却并非如此。事实上，与预期相反，极外平流层低层的臭氧持续减少（自 1998 年以来减少了 5%）。其原因尚不清楚，但建议的原因包括大气动力学的变化或短寿命活性碘和氯物质的丰度增加。我们将利用综合模型研究和对平流层下部的短寿命氯物质进行新的有针对性的观察来调查这种持续消耗的原因。虽然《蒙特利尔议定书》控制了长寿命消耗臭氧层物质的生产，但卤化物的情况却并非如此。寿命非常短的物质（VSLS，寿命<6 个月），基于这样的信念：它们的数量或持久性不足以产生影响。最近的观察表明，情况并非如此，几种气体（CH2Cl2、CHCl3）的大气丰度显着增加，这主要是由于亚洲排放量的增长。 2021 年夏季，美国将在日本开展大型飞机行动，提供有关这些短命物种的排放物如何通过亚洲夏季季风 (ASM) 到达平流层的重要新信息。 UEA 将通过在台湾和马来西亚进行有针对性的表面观测来补充 ACCLIP 活动，这将有助于限制氯排放。这些观测结果将与利兹和兰卡斯特的详细而全面的 3D 建模研究相结合，利兹和兰卡斯特拥有世界领先的专业知识和工具用于研究大气中的氯和碘。该模型将使用离线化学输运模型（CTM）（非常适合解释观测结果）和耦合化学-气候模型（CCM）（研究化学动力学反馈和未来预测所需）。关于气体如何受重力分离影响的新观察将用于测试大气环流变化的模型描述。 CTM 还将以“反向”模式使用，以将人为 VSLS 的观测追溯到其地理源区域。这些模型将用于量化平流层的短寿命氯和碘物质的通量，并确定它们对平流层低层臭氧趋势的影响。动态变化的影响将使用 CTM 进行量化，并使用 CCM 确定其驱动因素。将使用用于根据观测得出臭氧减少趋势的相同统计模型（包括动态线性模型（DLM））对模型结果进行分析。总体而言，模型实验的结果将被综合以了解平流层低层臭氧持续减少的情况。然后，这些信息将用于改进对臭氧未来如何演变的预测，这将在专家合作伙伴的合作下反馈到政策制定过程（《蒙特利尔议定书》）。该项目的结果将为未来的国际评估提供重要信息，例如WMO/UNEP 和 IPCC 报告。

项目成果

Atmospheric impacts of chlorinated very short-lived substances over the recent past - Part 2: Impacts on ozone

近期氯化极短寿命物质对大气的影响 - 第 2 部分：对臭氧的影响

• DOI: http://dx.10.5194/acp-23-13701-2023
• 发表时间: 2023
• 期刊: Atmospheric Chemistry and Physics
• 影响因子: 6.3
• 作者: Bednarz E

Description and evaluation of the new UM-UKCA (vn11.0) Double Extended Stratospheric-Tropospheric (DEST vn1.0) scheme for comprehensive modelling of halogen chemistry in the stratosphere

用于平流层卤素化学综合建模的新 UM-UKCA (vn11.0) 双扩展平流层-对流层 (DEST vn1.0) 方案的描述和评估

• DOI: http://dx.10.5194/gmd-2022-215
• 发表时间: 2022
• 作者: Bednarz E

Comment on "Observation of large and all-season ozone losses over the tropics" [AIP Adv. 12, 075006 (2022)]

对“热带地区大面积全季节臭氧损失的观察”的评论 [AIP Adv.

• DOI: http://dx.10.1063/5.0121723
• 发表时间: 2022
• 期刊: AIP Advances
• 影响因子: 1.6
• 作者: Chipperfield M

Anthropogenic Chloroform Emissions from China Drive Changes in Global Emissions

中国人为氯仿排放推动全球排放变化

• DOI: http://dx.10.1021/acs.est.3c01898
• 发表时间: 2023
• 期刊: Environmental Science & Technology
• 影响因子: 11.4
• 作者: An M

Atmospheric impacts of chlorinated very short-lived substances over the recent past. Part 1: the role of transport

最近氯化的寿命非常短的物质对大气的影响。

• DOI: http://dx.10.5194/acp-2022-34
• 发表时间: 2022
• 作者: Bednarz E