Theoretical Studies of Unbalanced Motions and Nonlinear Hadley Circulations in the Atmosphere

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The project will investigate aspects of unbalanced dynamics relevant to the tropical and extratropical atmosphere. Unbalanced motions, by definition, result when the balance between major geophysical forces (e.g., the pressure-gradient and Coriolis forces) is perturbed. The adjustment, or reestablishment of equilibrium, is accompanied by transient motions and/or wave propagation, such as gravity waves, inertial instability, etc. Dr. Dunkerton (Northwest Research Associates, Bellevue, Washington) will extend the analysis of inertial adjustment (resulting in zero potential vorticity in the adjusted region) from axisymmetric 2D flow configurations to non-symmetric 3D flows perturbed by Rossby waves in the winter hemisphere. Dr. Dunkerton will also investigate the triggering of deep moist tropical convection by gravity waves and other transient motions that are excited in the balance-restoring processes. The role of SST gradients and curvature in forcing the tropical Hadley circulation will also be analyzed. The project will advance our understanding of fundamental dynamical processes operative in atmosphere, and contribute to improved modeling of dynamical interactions between the hemispheres, triggering of deep convection, and ocean-atmosphere coupling (via the Hadley circulation).