Equilibrium Tropical Cyclone Size In Radiative-Convective Equilibrium

Tropical cyclone size remains an unsolved problem in tropical meteorology, yet size plays a significant role in the damage caused by tropical cyclones due to wind, storm surge, and inland freshwater flooding. This work explores the physical determinants of tropical cyclone size and structure in a highly-idealized state of axisymmetric radiative-convective equilibrium (RCE) governed by only four external thermodynamic parameters, which are shown to modulate the storm structure primarily via modulation of the potential intensity.

We find that the equilibrium radial wind profile scales primarily with the ratio of the potential intensity to the Coriolis parameter, matching the prediction for the scaling of the theoretical upper bound on tropical cyclone size embedded within prevailing axisymmetric tropical cyclone theory. The inner core structure is then modulated predominantly by a single non-dimensional parameter given by the ratio of this storm radial length scale to the parameterized eddy radial length scale. The far outer region is modulated by a second non-dimensional parameter embedded in a simple slab boundary layer outer wind model that assumes convection is absent. Finally, the Rossby deformation radius is shown not to be fundamental to equilibrium structure.