Cloud‐Radiation Feedback Facilitates Secondary Eyewall Formation of Tropical Cyclones

Abstract

Secondary eyewall formation (SEF) is an important topic in tropical cyclone (TC) dynamics owing to its significant influences on TC intensity and size (Houze et al., 2007;Kuo et al., 2009;Sitkowski et al., 2011;Willoughby, 1990). Typically, SEF possesses a secondary convective ring and an associated secondary low-level tangential wind maximum outside the primary eyewall (Willoughby et al., 1982), which is governed by internal dynamics but is also influenced by environmental forcings. Due to the complexity of the physical processes involved, the prediction of SEF remains a big challenge (Hazelton et al., 2018;Kossin & Sitkowski, 2009). SEF involves multi-scale internal processes, including but not limited to: the beta-skirt axisymmetrization of turbulent scale perturbations (Terwey & Montgomery, 2008); the interaction of vortex Rossby wave with vortex mean flow (Montgomery & Kallenbach, 1997;Qiu et al., 2010); the rapid filamentation effect in promoting moat region between two eyewalls (Rozoff et al., 2006); the balanced response to diabatic heating released by outer rainbands (ORBs) with enhanced inertial stability outside the primary eyewall (Rozoff et al., 2012); the unbalanced boundary layer (BL) dynamics (