A comparison of axisymmetric and three-dimensional hurricanes in an idealized framework

The goal of this work is to understand the similarities and differences between axisymmetric and three-dimensional hurricanes. To begin we consider a quiescent environment on an f-plane using an initially 'moist-neutral' thermodynamic sounding. Simulations are performed using the CM1 model (Bryan and Rotunno 2009) in both axisymmetry and 3D using identical horizontal and vertical grid spacing configurations. At this stage, simulations have been performed at horizontal grid spacing of 7.5 km and vertical grid spacing of 625 m. We find in agreement with some previous works that the quasi-equilibrium intensity is somewhat stronger in axisymmetry (maximum axisymmetric tangential winds 70 vs 62 m/s), but maximum sustained wind strengthens similarly in both models to day 5 at 55 m/s. A tangential momentum budget confirms the recently articulated spin up mechanism that occurs in the boundary layer but also highlights the contribution of the asymmetric eddy processes.

As the principal spin up of the inner core occurs in the boundary layer which is not well represented at the current resolution, additional experiments and analyses are conducted that resolve the unbalanced dynamics in the boundary layer and highlight the dynamical and thermodynamical role of the asymmetric eddy processes.