Dynamics and Maintenance of the Intertropical Convergence Zones

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The Intertropical Convergence Zones (ITCZs) are climatological features in the earth's atmosphere that are intimately tied to both the tropical large-scale meridional (Hadley) circulation and the low-latitude surface circulation. The ITCZs drive the meridional circulation cells which transport momentum and excess heat from the tropics to midlatitudes, thereby affecting the baroclinity of the midlatitudes and hence climate. In addition, the eastern Pacific ITCZ appears to play a role in the large El Nino/Southern Oscillation climate fluctuations. Yet the dynamics and energetics of the processes maintaining the Intertropical Convergence Zones are poorly understood. This study examines the maintenance of the ITCZ phenomenon and the associated large-scale circulation, using a General Circulation Model and a simplified 3-layer model of the tropical atmosphere. The PI will explore how the surface boundary heating (sea surface temperature) and orography effect the location, strength, energetics and dynamics of the ITCZ through a carefully designed set of GCM experiments with increasingly complicated forcing. A 3-layer model of the tropical atmosphere will be constructed and employed to facilitate in the interpretation of the GCM experiments (this model will explicitly resolve the boundary layer and the free baroclinic tropical tropospheric circulations). The results will help to better define the relationship between the ITCZ and large-scale meridional and surface circulations, and hence contribute to our knowledge of the global climate.