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预计将影响平流层水蒸气和臭氧的恢复，对地面温度、降水和风有直接影响。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，用分析理论来验证模型模拟，识别和纠正模型偏差，并建立严格的测试来评估它们对气候预测的适用性。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际经验。这个项目将把平流层传输的理论、模型和观测联系起来。布鲁尔-多布森环流描述了质量和微量气体通过平流层的传输。与化学过程相一致，它设定了水蒸气和臭氧在中间大气中的分布。模式几乎一致地预测布鲁尔-多布森环流将随着人为强迫的增加而增加，但由于翻转的时间尺度较慢(在数年左右)，无法直接观测到该环流。然而，对“空气年龄”的现场和基于卫星的估计，并不能很好地检测到运输的变化。“空气年龄”是一种测量从地表到平流层的运输时间的指标，可以通过对痕量气体的观测来估计。一些人甚至暗示发行量会减弱，尽管很大的不确定性意味着模型趋势并不矛盾。该项目的第一个目标是利用三维大气模型建立平流层环流和年龄分布之间的联系。特别是，年龄的纬度结构可以通过对二氧化碳或SF6等微量气体的测量直接计算出来，它将与平均质量循环有关，这是在气候模型积分中诊断的。第二个目标是利用这些洞察力在数值模式中评估平流层输送，将动力核心的标准测试与环流的气候学特性联系起来。对年龄运输的理论限制将被用来发现气候模型因其在表示环流和/或示踪剂运输方面的不足而产生的偏差。第三个也是最后一个目标是在气候变化的背景下评价新的示踪剂运输诊断方法。

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.