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

预计大气环流因人为强迫而发生的变化将影响平流层的水汽和臭氧恢复，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。本研究将制定策略，用分析理论验证模型模拟，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应性。该项目还将支持两名研究生的教育和培训。为他们提供发展大气环流的物理理解和高性能科学计算的实践经验的机会。这个项目将把平流层运输的理论、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输送。与化学过程相一致，它设定了水蒸气和臭氧在中层大气中的分布。模型几乎一致地预测布鲁尔-多布森环流会因人为强迫而增加，但由于翻转的缓慢时间尺度（以年为数量级），不能直接观察到环流。然而，对“空气年龄”的就地估算和基于卫星的估算并不能可靠地探测到运输的变化。“空气年龄”是一种测量从地表到平流层运输时间的方法，可以通过对微量气体的观测来估算。有些人甚至认为环流正在减弱，尽管巨大的不确定性意味着模式趋势并非不一致。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与年龄分布之间的联系。特别是，年龄的纬度结构可以直接从CO2或SF6等微量气体的测量中计算出来，它将与在气候模式整合中诊断出来的平均质量环流有关。第二个目标是利用这些见解在数值模式中评估平流层运输，将动力核心的标准测试与环流的气候特性联系起来。对年龄传输的理论限制将用于检测气候模式中由于对环流和/或示踪剂传输的表述不足而产生的偏差。第三个也是最后一个目标是在气候变化的背景下评估新的示踪剂运输诊断。

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.