The Role of Radiation in Accelerating Tropical Cyclogenesis in Idealized Simulations

Recent numerical modeling studies indicate the importance of radiation in the transformation from a tropical disturbance to a tropical depression, a process known as tropical cyclogenesis. This paper employs a numerical modeling framework to examine the sensitivity to radiation in idealized simulations for different initial vortex strengths, and in doing so highlights when during tropical cyclogenesis radiation is most important. It is shown that all else being equal, a stronger initial vortex reduces the impact that radiation has on accelerating tropical cyclogenesis. We find that radiation's primary role is to moisten the core of a disturbance through nocturnal differential radiative forcing between the disturbance and its cloud-free surroundings, and after sufficient moistening occurs over a deep layer and the winds are sufficiently strong at the surface, radiation no longer plays as significant a role in tropical cyclogenesis.