Cloud-Radiation Feedback Facilitates Secondary Eyewall Formation of Tropical Cyclones

Recent studies show that the formation of outer rainbands (ORBs) is essence to secondary eyewall formation (SEF) of tropical cyclones (TCs). This study reveals that cloud-radiation feedback (CRF) facilitates SEF of TCs by promoting the formation of ORBs and their stratiform sectors. In detail, CRF engenders an upper-level anomalous radiative warming in the outer-core region, which induces a secondary circulation that accelerates the release of microphysical heating above the freezing level. The enhanced upper-level latent heating further promotes the outer-core convection and the top-down development of the ORBs. Moreover, CRF promotes a broader stratiform precipitation area and stronger stratiform heating profiles of the ORBs, which forces convective updrafts at the radially inward edge of the stratiform precipitation area and eventually leads to SEF. On the contrary, when the anomalous radiative warming is removed, the organization of ORBs and the development of stratiform precipitation are suppressed due to the absence of the radiation-induced upper-level secondary circulation, thus inhibiting SEF.