Mature typhoon “cloud gyro” model and numerical simulation study

Abstract

Due to the coarse temporal resolution of the best track databases for typhoons, some small-scale characteristics of typhoon motion have been neglected. In order to reveal the fine features of typhoon motion, the dense cloud within the radius of maximum wind (RMW) of mature typhoons, defined as a “cloud gyro” that simultaneously spins around its own rotational axis and precesses around the vertical axis, is approximated to a rigid body. Based on the principles of gyrodynamics, the derived mathematical model of a typhoon track indicates that typhoon movement is composed of translational motion governed by the steering flow and superimposed precessional motion that manifests as the inherent characteristics of typhoon tracks, especially with the external torque. High temporal resolution numerical simulation of a real case verifies the conclusion of this study, which is that the smaller the RMW, the larger the tangential wind speed or the larger the external torque, and the more obviously precessional motion manifests.