| Hurricane intensity is an issue of great importance and broad public interest. At the same time it is an enormously complex problem and we cannot yet accurately predict the maximum intensity a developing hurricane will attain. In order to improve our insight into the mechanisms that control hurricane intensity, this thesis proposes a simplified theoretical and numerical model, based on a dry thermodynamic framework.;The motivation for this approach stems from the axisymmetric hurricane intensity theory of Emanuel (1986). Hurricanes are sustained by the energy flux supplied from the ocean to the atmosphere, and in a moist environment this flux is a combination of latent and sensible heat fluxes. Emanuel's hurricane intensity theory includes the latent heating due to moisture implicitly, within the definition of entropy. Thus if the sensible heat flux is enhanced to compensate for the missing latent heat source, the same theoretical considerations are valid for a dry framework. Using a non-hydrostatic, axisymmetric numerical model, it is demonstrated here that, indeed, moisture is not necessary to produce hurricane-like storms, either numerically and theoretically.;The mechanisms that control intensity are investigated by performing a large number of experiments for both dry and moist conditions. In both environments, simulated storms are morphologically similar, but always exceed the theoretical intensity limit of Emanuel. It is shown here that if the crude theoretical estimate of the boundary layer entropy budget is replaced with its numerically diagnosed structure, including eddy flux terms, the modified intermediate theory successfully predicts storm intensity in all cases. Therefore, a complete theory of hurricane intensity should follow from a sufficiently accurate theory for the boundary layer entropy budget. Finally, the dry framework should prove useful for the study of polar lows, dust devils and hurricanes in a cold Earth scenario. |
