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Title: The Critical Role of Cloud–Infrared Radiation Feedback in Tropical Cyclones
Abstract: While idealized studies suggest that tropical convective cloud systems are sensitive to feedbacks with atmospheric radiative heating, we remain highly naïve to the role of such feedbacks in the evolution of real tropical cyclones in nature (TCs; e.g., hurricanes, typhoons). We seek to address this gap here. To do so, we conduct a set of large-domain numerical model simulations to assess the impact of cloud–longwave feedback in the development of Supertyphoon Haiyan (2013) and Major Hurricane Maria (2017). In both storms, we find that cloud–longwave radiation feedback is critical to accelerating genesis and rapid intensification (RI), and hence is essential to explaining the intensity that these two storms ultimately reached prior to making landfall. This longwave radiative feedback manifests in locally amplified longwave warming at and below the bases of deep, optically opaque clouds – an effect often termed the “cloud greenhouse effect.” The additional buoyancy provided by this cloud greenhouse effect promotes or accelerates the upscale organization of convective clouds, and the intensification of the tropical cyclone's circulations. These results imply that cloud–longwave radiation feedback is likely important for increasing the global number of strong TCs each year. Furthermore, the findings imply that addressing the shortcomings in numerical forecast models linked to cloud–radiation feedback may help break the longstanding deadlock in TC intensity prediction.