An air-sea interaction theory for tropical cyclones. Part II: evolutionary study using a nonhydrostatic axisymmetric numerical model.

In Part I of this study an analytical model for a steady-state tropical cyclone is constructed on the assumption that boundary-layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex. The reversible thermodynamics implied by this assumption allows the mature storm to be throught of as a simple Carnot engine. The numerical experiments show that as a result of a finite-amplitude air-sea interaction instability a hurricane-like vortex may indeed amplify in an atmosphere which is neutral to cumulus convection and attain an intensity and structure. We examine in detail the model's heat budget which confirms the crucial importance of boundary-layer processes in controlling the structure and evolution of the vortex. We also confirm the conjecture made in Part I that, within a large-scale limit, the horizontal size of the mature tropical cyclone is determined by that of the initial disturbance.-from Authors