The Moisture-Convection Feedback Can Lead to Spontaneous Tropical Cyclogenesis

Abstract

In contrast to prevailing knowledge, Ram\'irez Reyes and Yang (2021) showed that tropical cyclones (TCs) can form spontaneously without moisture-radiation and surface-flux feedbacks in a cloud-resolving model (CRM) simulation. Here we ask, why? Thirteen 3D cloud-resolving simulations show that the moisture-convection (MC) feedback can effectively lead to spontaneous TC genesis and intensification in the absence of radiative and surface-flux feedbacks. In the MC feedback, a moister environment favors new deep convective events that further moisten the environment, leading to aggregation of deep convection. The impact of the MC feedback on TC genesis and intensification occurs in two distinct time scales: a short time scale set by detrainment moistening the environment (a few hours) and a long time scale (17 days) due to subsidence drying. The hours-long time scale of detrainment suggests that the MC feedback is an efficient process relevant to TC genesis in the real world.