Large-scale dynamics of tropical cyclone formation associated with the ITCZ breakdown

Abstract

This study examines the formation of tropical cyclones (TCs) from the large-scale perspective. Using the nonlinear dynamical transition framework recently developed by Ma and Wang, it is shown that the large-scale formation of TCs can be understood as a result of the principle of exchange of stabilities in the barotropic model for the intertropical convergence zone (ITCZ). Analyses of the transition dynamics at the critical point reveal that the maximum number of TC disturbances that the Earth's tropical atmosphere can support at any instant of time has an upper bound of ∼12 for current atmospheric conditions. Additional numerical estimation of the transition structure on the central manifold at the critical point of the ITCZ model confirms this important finding, which offers an explanation for a fundamental question of why the Earth's atmosphere can support a limited number of TCs globally each year.