Dynamics of Tropical Cyclones and the Hadley Circulation

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Several aspects of tropical dynamics that are still poorly understood are the potential vorticity mixing processes in hurricanes and the details of the convective-scale generation of potential vorticity in both hurricanes and the Intertropical Convergence Zone (ITCZ). Under this award, Dr. Schubert seeks to increase dynamical understanding and to improve the accuracy of numerical simulations of tropical circulations. Within hurricanes, recent work has shown that there are smaller-scale, seemingly unrelated, phenomena associated with potential vorticity mixing such as mesovortices and polygonal eyewalls which have some common characteristics. Dr. Schubert will employ a hierarchy of theoretical and numerical models, from a nondivergent barotropic model to one that employs the nonhydrostatic, "full-physics" equations to explore them. The exciting new aspect of this study will be the incorporation of moist processes in the models. A second area of investigation is to use a version of the full physics model to explore aspects of the Hadley circulation and the ITCZ. Of particular interest is the study of the role of cloud ice processes in the circulations and the sensitivity to the nature of the cloud microphysics parameterizations employed in the models. This research, while highly theoretical and conducted with idealized models, is critical to advance the understanding of the basic dynamics of tropical circulations.