Equilibrium Tropical Cyclone Size in an Idealized State of Axisymmetric Radiative-Convective Equilibrium

Tropical cyclone size remains an unsolved problem in tropical meteorology, yet size plays a significant role in the potential damage caused by tropical cyclones due to both wind damage and storm surge. The Bryan Cloud Model (CM1) is employed to explore tropical cyclone size in a highly idealized environment: axisymmetric geometry with constant sea surface temperature, constant Coriolis parameter, zero background vertical wind shear, and constant tropospheric radiative cooling. Each simulation is initialized with the radiative-convective equilibrium (RCE) vertical profile of temperature and water vapor calculated from the analogous three-dimensional simulation on a domain small enough to inhibit convective aggregation. This modeling framework is then used to assess the sensitivity of both transient and equilibrium tropical cyclone size, defined as the radius of vanishing winds (r0), to both model and physical parameters. We find here that storm size tends to expand to a single equilibrium size that corresponds with the theoretical upper bound defined in Emanuel (1986). This size may also be modulated by the turbulence parameterization, but it is found to be largely insensitive to the initial condition. Potential implications for real storms in nature are discussed.