The Role of Convective Heating in Tropical Cyclone Vortex Evolution - Idealized Three-Dimensional Full-Physics Model Simulations

Many previous studies have discussed the barotropic instability in the vorticity ring based on the linear stability theory in the barotropic framework. Both hollowness and thickness of a vorticity ring have been found critical in determining the growth rate of barotropic instability. It has been suggested that the vorticity rings in the typhoon eyewall are often barotropically unstable and end up with persistent crystals or a monopole. However, observations or simulations with more sophisticated physical processes have shown that a vorticity ring structure in a typhoon can sustain for a long period of time.

In this study, a full-physics model is used to construct idealized simulations (3-km grid spacing) in a quiescent background field. We investigate the simulated vortex with a potential vorticity (PV) ring present at the mid-lower levels during the integration. To evaluate the impact of convective heating on the PV ring evolution, sensitivity experiments are carried out by artificially increasing or decreasing the diabatic heating rate in the microphysics scheme.

The PV ring with reduced convective heating relaxes to a monopole at first and then recovers the ring structure during later hours of the integration. In contrast, the PV ring with increased convective heating rate can remain the ring structure during the entire integration. The PV budget analysis is provided for a quantitative evaluation of the influence of convective heating on the evolution of the PV ring. Results from this work provide some new physical insight into the role of convective heating on the dynamic evolution of eyewall vortex.