EAPS

Title: The role of radiative-convective feedbacks in tropical cyclone formation in numerical simulations

Interactions between convection, moisture, clouds, and radiation can cause tropical convection to “self-aggregate" in idealized numerical simulations. Here, we explore the role of these processes in tropical cyclone formation. First, we perform idealized numerical simulations of rotating radiative-convective equilibrium with a cloud-resolving model, in which, rather than using a weak vortex or moist bubble to initialize the circulation, we allow a circulation to form spontaneously in a homogeneous environment. We compare the resulting tropical cyclogenesis to non-rotating self-aggregation. We find that in the initial development of a broad circulation, the feedback processes leading to cyclogenesis are similar to the initial phase of non-rotating aggregation. Sensitivity tests in which the degree of interactive radiation is modified are also performed to determine the extent to which the radiative feedbacks that are essential to non-rotating self-aggregation are important for tropical cyclogenesis. Radiative feedbacks are found to accelerate cyclogenesis but are not strictly necessary for it to occur.

We then explore the tropical cyclogenesis and intensification processes in realistic historical simulations of tropical cyclones with five high-resolution global climate models. We track the formation and evolution of tropical cyclones in the climate model simulations and apply a moist static energy budget analysis both along the individual tracks and composited over many tropical cyclones. We find that the genesis processes, in terms of the contributions to the moist static energy variance budget, are qualitatively similar across all models and to the cloud-resolving model simulations.