Stratospheric and Tropical Influences on the Mid-Latitude Circulation Response to Rising Greenhouse Gases

该项目旨在了解温室气体浓度上升导致的全球平均温度上升将如何影响北方和南半球中纬度地区的急流和风暴路径（中纬度锋面系统的典型路径）。 以往对全球变暖模拟的研究发现，随着温度的升高，两个半球的急流和风暴轨迹都向各自的两极移动，但这种移动的动力学机制还没有得到很好的理解。 此外，不同模型的模拟结果在变化幅度上并不一致。 该项目涉及的一个问题是平流层动力学在产生变化方面的作用（特别是在北方半球），以及平流层增强的代表性（例如，在模型计算网格上平流层的更多层次）导致变化的质量差异的程度。 所涉及的第二个问题是南半球急流和风暴路径变化受热带过程影响的程度，这项工作的更广泛影响来自于更好地了解大气环流对温室气体引起的变暖的反应的实用价值。 急流和风暴路径的变化可以影响中纬度地区的气候，向极的变化可能导致干燥的副热带沉降带的扩大。 该项目还试图了解不同模式在环流变化方面的差异，并可能有助于减少未来气候变化预测的不确定性。 此外，这项工作将支持和培训一名研究生，从而为这一领域的未来劳动力提供支持。

This project seeks to understand how increases in global-mean temperature due to rising greenhouse gas concentrations will affect the jet stream and storm tracks (the typical paths of midlatitude frontal systems) found in the midlatitudes of the Northern and Southern Hemisphere. Previous studies of global warming simulations have found that jet streams and storm tracks in both hemispheres shift towards their respective poles with rising temperature, but the dynamical mechanisms for the shifts are not well understood. Moreover, simulations from different models do not agree as to the magnitude of the shifts. One issue addressed in this project is the role of stratospheric dynamics in producing the shifts (particularly in the Northern Hemisphere), and the extent to which enhanced representation of the stratosphere (more levels in the stratosphere on the model computational grid, for instance) leads to qualitative differences in the shifts. A second issue addressed is the extent to which the jet and storm track shifts in the Southern Hemisphere are influenced by tropical processes.The broader impacts of the work come from the practical value of an improved understanding of the atmospheric circulation response to greenhouse gas-induced warming. Shifts in the jet streams and storm tracks can affect regional climate in the midlatitude, and poleward shifts may lead to widening of the dry subtropical subsidence belts. The project also seeks to understand differences in circulation change from different models, and may help to reduce uncertainty in projections of future climate change. In addition, the work will support and train a graduate student, thereby providing for the future work force in this area.