Collaborative Research: Stratospheric Age in a Changing Climate: Connecting Theory, Models, and Observations

大气环流对人为强迫的响应变化预计将影响平流层水汽和臭氧的恢复，并对地表温度、降水和风产生直接影响。政策制定者和公众依赖于这些变化的模型预测。这项研究将制定策略，以验证模型模拟与分析理论，识别和纠正模型的偏差，并建立严格的测试，以评估其适应气候预测。该项目还将支持两名研究生的教育和培训。为他们提供机会，发展对大气环流的物理理解和高性能科学计算的实践经验。该项目将连接理论，建模和平流层传输的观测。布鲁尔-多布森环流描述了物质和微量气体通过平流层的传输。与化学过程相一致，它决定了水蒸气和臭氧在中层大气中的分布。模式几乎一致预测布鲁尔-多布森环流增加响应人为强迫，但不能直接观察到的流通，由于翻转的时间尺度缓慢（在几年的顺序）。然而，对“空气年龄”的实地和卫星估计，即从地面到平流层的迁移时间的测量，可以通过对痕量气体的观测来估计，并不能有力地探测到迁移的变化。有些人甚至认为环流减弱，尽管很大的不确定性意味着模式趋势并不一致。该项目的第一个目标是建立平流层环流和年龄分布与三维大气模型之间的联系。特别是，年龄的纬度结构，可以直接从测量的微量气体，如二氧化碳或SF6计算，将涉及到平均环流的质量，这是诊断在气候模式集成。第二个目标是利用这些见解来评估数值模型中的平流层传输，将动力核心的标准测试与环流的气候学特性联系起来。年龄运输的理论约束将被用来检测气候模型中的偏差所产生的缺陷，在他们的代表性的流通和/或示踪剂运输。第三个也是最后一个目标是在气候变化的背景下评估新的示踪剂-迁移诊断。

Changes in the atmospheric circulation in response to anthropogenic forcing are expected to affect stratospheric water vapor and ozone recovery, with direct effects on surface temperatures, precipitation, and winds. Policy makers and the public rely on model projections of these changes. This research will develop strategies to validate model simulations with analytic theory, to identify and correct model biases, and to establish rigorous test to assess their fitness for climate projection. This project will also support the education and training of two graduate students. providing them the opportunity to develop a physical understanding of the atmospheric circulation and practical experience with high performance scientific computing. This project will connect theory, modeling, and observations of stratospheric transport. The Brewer-Dobson Circulation describes the transport of mass and trace gases through the stratosphere. In concert with chemical processes, it sets the distribution of water vapor and ozone through the middle atmosphere. Models nearly unanimously predict the Brewer-Dobson Circulation to increase in response to anthropogenic forcing, but the circulation cannot be observed directly, due to the slow time scale of overturning (on the order of years). In situ and satellite-based estimates of the "age of air," a measure of the transport time from the surface to stratosphere which can be estimated from observations of trace gases, however, do not robustly detect a change in transport. Some even suggest a weakening of the circulation, although large uncertainties imply that model trends are not inconsistent. The first goal of this project is to establish a connection between the stratospheric circulation and age distributions with three-dimensional atmospheric models. In particular, the latitudinal structure of age, which can be calculated directly from measurements of trace gases such as CO2 or SF6, will be related to the mean circulation of mass, which is diagnosed in climate model integrations. The second goal is to use these insights to evaluate stratospheric transport in numerical models, connecting standard tests of dynamical cores to the climatological properties of the circulation. Theoretical constraints on age transport will be used to detect biases in climate models arising from deficiencies in their representation of the circulation and/or tracer transport. The third and final goal is to evaluate the new tracer-transport diagnostics in the context of climate change.