Why is Lower Stratospheric Ozone Not Recovering?

为什么平流层低层臭氧没有恢复？

基本信息

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

项目摘要

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.

平流层臭氧的耗竭允许更大剂量的有害太阳能紫外线（UV）辐射到达表面，从而导致人类皮肤癌和白内障的增加以及其他影响，例如作物损害。臭氧还会影响地球的辐射平衡，尤其是下层平流层（LS）中的臭氧耗竭会产生重要的气候强迫。虽然大多数长期消耗臭氧的物质（例如ODS，例如氯氟化合物，CFCS）现在受到联合国蒙特利尔方案的控制，其丰度正在缓慢下降，但围绕臭氧层回收率的速率仍然存在很大的不确定性。尽管在平流层和南极的上部已经检测到了恢复的迹象，但在中间和低纬度的平流层下，情况并非如此。实际上，与预期相反，这种外极下层平流层中的臭氧持续下降（自1998年以来，最高可达5％）。尚不清楚的原因，但建议的原因包括大气动力学的变化或短寿命的反应性碘和氯种的丰度增加。我们将使用全面的建模研究和对较低平流层中短寿命的氯物质进行新的靶向观察研究来研究这种持续耗竭的原因。虽然蒙特利尔协议控制了长期寿命的ODS的产生，但事实并非如此非常短暂的物质（VSL，寿命<6个月），基于这样的信念，即它们不会足够丰富或持久而无法产生影响。最近的观察结果表明，由于亚洲排放的增长，几种气体的大气丰度显着增加（CH2CL2，CHCL3）。 2021年夏季在日本举行的一项美国大型飞机运动将提供有关这些短暂物种的这些排放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察来补充Acclip运动，这将有助于限制氯排放。这些观察结果将与利兹和兰开斯特的详细且全面的3D建模研究结合在一起，他们拥有世界领先的专业知识和工具用于研究大气氯和碘。该建模将使用离线化学传输模型（CTM），理想的解释观测以及耦合的化学气候模型（CCM），该模型（CCM）是研究化学动力反馈和未来预测所需的。关于如何受重力分离影响气体如何影响的新发现，将用于测试大气循环中变化的建模描述。 CTM还将以“反向”模式使用，以将人为VSL的观察结果追溯到其地理源区域。这些模型将用于量化短寿命的氯和碘物种的通量到平流层，并确定它们对下层平流层臭氧趋势的影响。动态变异性的影响将使用CTM和使用CCM确定的驱动因素来量化。将使用与观测值（包括动力学线性模型（DLM））相同的统计模型来分析模型结果。总体而言，模型实验的结果将被合成，以理解下层平流层臭氧的持续下降。然后，这些信息将用于改善臭氧如何发展的未来预测，该预测将与专家合作伙伴的合作融入政策制定过程（蒙特利尔协议）。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。