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）是气候的关键要素，因为它决定了对流层面上方的臭氧（O3），水蒸气和气溶胶的运输和寿命，从而显着影响地球的辐射预算。增强BDC将影响对流层和下层平流层（UTL）的微量气体预算，因此对气候可能产生至关重要的后果。最近，增强BDC已被证明可以调节O3的向下通量，这反过来又影响了气候和人类健康。这就是了解季节到衰老时间尺度上的BDC变异性是对自然变异性和人为变化趋势的可靠检测和属性的先决条件。然而，在当前气候模拟中通常无法可靠地表示BDC的可变性，施放与测量值的比较。我们旨在评估BDC对UTLS微量气体痕量气体分布以及对气候的自然变异性和长期人为作用的趋势的影响，并分析动态机制，从而导致模型差异。该项目将既定的诊断工具，与重新分析驱动的拉格朗日传输模型和耦合化学气候模型的模拟结合在一起，以及用于研究BDC变化的可用观察结果以及对UTLS O3的相关影响。为了实现这些主要目标，工作计划具有三个工作包：（1）对BDC的自然变异性和人为引起的趋势进行调查，（（2）理解涉及的动态机制，以及（3 3）评估BDC对向下o3 flux的影响的影响。使用拉格朗日运输模型（蛤）和化学气候模型（EMAC）的模拟。对观察与模拟的比较是披露模型准确捕获BDC变异性的能力的先决条件。然后，回归分析的使用将使BDC和UTLS O3分布中的可变性和长期趋势的属性与不同的攀岩变异性模式相关。要研究动态机制，我们提出了三种类型的敏感性实验，除了可用的模拟。这些实验将以某种方式进行，使它们能够披露由不同的强迫和模型观察差异引起的BDC变化所涉及的动态机制。在本文中，BDC变化对向下O3磁通的影响以及与Clams驱动的Clams驱动的长期模拟对向下O3磁通的影响以及相关的气候效应。下向下的O3通量将使用预算方法在最低平流层中的O3进行量化。回归分析将将O3通量的变异性归因于不同气候变化模式，严重影响气候和空气质量。