Dynamics of the Midlatitude Circulation and Implications for a Changing Climate

该项目研究了与大气环流的两个基本方面有关的动力过程：中纬度急流的中心纬度及其伴随的风暴路径和地面西风，以及中纬度对流层顶的高度和锐度。这项工作同时考虑了气候平均急流位置和对流层顶高度，以及由于温室气体导致的大气总体变暖而可能发生的位置和高度的变化。对急流纬度的研究将特别考虑与风暴路径相关的涡流驱动急流与哈德利环流极地侧翼发现的副热带急流之间的相互作用。对流层顶的研究将考虑大气辐射平衡在确定其高度和锐度方面的重要性，而不是与风暴路径有关的波动大气运动的混合效应。急流纬度和对流层顶高度密切相关，因为之前的研究表明，两者都可以相互影响。研究将通过大气模型的层次结构进行，从最简单的数值框架开始，逐步发展到全面的、最先进的气候模型。如果这项工作成功，将有助于更好地理解气候系统及其对强迫变化的反应，从而有助于改进对温室气体浓度增加的社会影响的预测。这项工作还将通过主要调查员的教学和外联活动产生更广泛的影响。此外，该项目还将资助和培训一名研究生，从而培养未来大气环流和气候动力学领域的科学人才。

This project studies the dynamical processes responsible two fundamental aspects of the general circulation of the atmosphere: the central latitude of the midlatitude jet streams and their accompanying storm tracks and surface westerlies, and the height and sharpness of the midlatitude tropopause. The work considers both the climatological mean jet position and tropopause height, and the changes in position and height that are likely to occur due to the overall warming of the atmosphere by greenhouse gas increases. Research on the latitude of the jet streams will consider, among other things, the interaction between the eddy-driven jets associated with the storm tracks, and the subtropical jets found on the poleward flanks of the Hadley cells. Research on the tropopause will consider the importance of atmospheric radiation balance in determing its height and sharpness, rather than the mixing effect of wavy atmospheric motions associated with the storm tracks. Jet latitude and tropopause height are closely associated, as previous research shows that each can influence the other. Research will be conducted through a hierarchy of atmospheric models, starting from the simplest possible numerical framework and progressing to comprehensive, state-of-the-art climate models.The work will, if successful, lead to improved understanding of the climate system and its response to changes in forcing, and so contribute toward improved predictions of the societal impacts of increasing greenhouse gas concentrations. The work will also have broader impacts through the teaching and outreach activities of the principal investigators. In addition, the project will fund and train a graduate student, thereby providing for the future scientific workforce in the area of atmospheric general circulation and climate dynamics.