Influences of Asymmetric Convection on Vortex Alignment of Tropical Cyclones: Idealized Experiments

The classic theories on tropical cyclone (TC) intensification (i.e., CISK, WISHE) are based on the assumption of an axisymmetric and vertically aligned TC circulation. However, how the TC vortices align at various altitudes within a sheared environment is a challenging topic in the TC intensity change research. This study investigates vortex alignment in tropical cyclones (TCs) through two idealized experiments conducted under easterly vertical wind shears (VWS) of 6 m s⁻¹ and 10 m s⁻¹. Both experiments simulate TCs that  exhibit intensification simultaneously. While the onset of intensification hinges on the achievement of a vertically aligned vortex structure, the evolution of vortex tilt displays significant differences between the two cases. We find the crucial role of convective asymmetry, predominantly intensified on the downtilt side of the simulated TCs, in driving vortex alignment.On one hand, diabatic heating associated with the asymmetric convection directly aids in reducing the vortex tilt. On the other hand, this convective asymmetry generates counter-rotating gyres within the inner-core region. These gyres produce cyclonic vorticity downstream of the heating zone and anticyclonic vorticity downstream of the cooling zone, which obstructs vertical structure coupling. The interplay between these processes ultimately dictates the evolution of vortex tilt. This research emphasizes the importance of capturing convective processes to improve the  TC intensification prediction.