Dynamics of the Midlatitude Circulation and Implications for a Changing Climate

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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.