How are natural variability and anthropogenic forcings affecting the variability and trends in the Brewer-Dobson circulation and downward ozone flux?

自然变化和人为强迫如何影响布鲁尔-多布森环流和臭氧通量下降的变化和趋势？

• 批准号: 429838442
• 负责人: Dr. Mohamadou Diallo, Ph.D.
• 金额: --
• 依托单位: IEK-7: Stratosphäre
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429838442?language=en
• 关键词: How; natural; variability; anthropogenic; forcings

The Brewer-Dobson circulation (BDC) is a key element of climate as it determines the transport and lifetime of ozone (O3), water vapor and aerosol above the tropopause, which significantly affect the Earth’s radiation budget. A strengthening BDC will impact the trace gas budgets in the upper troposphere and lower stratosphere (UTLS) and, thus, may have crucial consequences for climate. Recently, a strengthening BDC has been shown to modulate the downward O3 flux which, in turn, impacts on both climate and human health. Thus, understanding the BDC variability on seasonal to decadal time scales is a prerequisite for a reliable detection and attribution of the natural variability and anthropogenically-forced trends. However, BDC variability is often not reliably represented in current climate simulations, casting comparisons with measurements into doubt.We aim to assess the impact of natural variability and long-term anthropogenically-forced trends in the BDC on the UTLS trace gas distribution and on climate, and to analyze the dynamical mechanisms, leading to model-observation differences. The project combines established diagnostic tools, simulations with a reanalysis-driven Lagrangian transport model and a coupled chemistry-climate model together with available observations for investigating BDC changes and the related impacts on UTLS O3. To achieve these major goals, the work plan has three work-packages: (1) Investigations of the natural variability and anthropogenically-induced trends in the BDC, (2) Understanding dynamical mechanisms involved, and (3) Evaluation of the impact of BDC changes on the downward O3 flux.Available multi-year time series of observations (incl. O3 and mean age of air) will be used for investigating the variability and long-term BDC changes in the simulations with the Lagrangian transport model (CLaMS) and chemistry-climate model (EMAC). This comparison of observations with simulations is a prerequisite for disclosing the models’ ability to accurately capture the BDC variability. The use of regression analysis will then enable an attribution of variability and long-term trends in the BDC and in UTLS O3 distributions to different modes of climate variability.To investigate the dynamical mechanisms, we propose three types of sensitivity experiments in addition to the available simulations. These experiments will be conducted in a way that they will enable to disclose the dynamical mechanisms involved in the BDC changes induced by different forcings, and model-observation discrepancies.Finally, the impact of BDC changes on downward O3 flux and related effects on climate will be assessed using the long-term simulation with CLaMS driven by the EMAC output data. The downward O3 flux will be quantified using a budget approach to model O3 in the lowermost stratosphere. Regression analysis will attribute the variability in O3 flux to different modes of climate variability that critically impact the climate and air quality.

Brewer-Dobson循环（BDC）是Climette的关键要素，因为臭氧（O3）的终生型tropopopause的运输和寿命会显着影响地球辐射预算（因此，UTLS）。对于气候的关键，可以使O3向下的通量进行模块化，从而对气候和人类健康产生影响。然而，在当前气候模拟中，BDC的变异性与疑问相比具有可靠的抑制作用。导致模型观察的差异。 ，工作计划的工作包：（1）对BDC nd（3）评估BDC变化对向下O3 Flux的影响的自然变异性和人为引起的趋势的调查。 （包括O3和平均空气年龄）将使用Sith Torangian运输EL（CLAM）和化学气候模型（EMAC）的长期BDC变化（EMAC）。模型对BDC和UTLS O3分布中的变异性和趋势的模型为不同的气候变化模式。为了研究动态机制，我们提出了除了可用的模拟外，还提出了敏感性。 BDC中涉及的动力学机制最终会改变BDC的影响O3通量的影响，并将使用EMAC输出数据来评估与气候的相关效果。使用预算方法在最低的平流层中进行量化。