Quasi‐Periodic Behavior of Tropical Cyclone Precursors and Its Phase Matching With the Insolation Diurnal Cycle

Abstract The formation of tropical cyclones (TCs) remains a significant scientific challenge. Here, we demonstrate that robust quasi‐periodic behavior (QPB) emerges during TC genesis with idealized numerical simulations. The QPB is an internal mode of the TC precursor, whose underlying mechanism is a convectively coupled inertia‐gravity oscillation. With typical environmental parameters and the spatial scale of TC precursors, the period of oscillation is around daily timescale. When the phase of the QPB and the solar diurnal cycle match, the coupling between the two oscillations accelerates TC genesis due to the state‐dependent responses of precursors to diurnal radiation. This research unveils a potentially important mechanism for TC genesis in the real world: the diurnal cycle partially strengthens the TC seeds with matched phases among those from natural variability. Thus, our results have significant implications for understanding TC dynamics and improving predictions.