The existence of concentric eyewall structure is a universal episode in intense tropical cyclones (TCs). The commonly-observed concentric eyewall replacement cycle (ERC) generally involves the following stages: secondary eyewall formation (SEF), inward contraction of the secondary eyewall, demise and replacement of the inner eyewall, and organization of a new substitute eyewall. The ERC process can render notable structure change and intensity fluctuation, which poses a challenge for forecaster. In this talk, Prof. Chen will examine the role of increased inner-core diabatic cooling in TC SEF and ERC by using idealized numerical simulation in WRF. The experiment with the low-level inner-core diabatic cooling increased is characterized by the low-entropy air and downward motion in the inner-core region whereas the convergence and active convective updrafts in the outer-core region. In collaboration with the favorable dynamic ambient conditions and unbalanced boundary layer dynamics induced by the outer rainbands, the concentric convective ring is triggered and contracts inward to replace the inner eyewall, and the deep-tropospheric radial outflows driven by the strong outward-directed agradient force give rise to a largely outward-tilted eyewall then, eventually forming a large-eyed storm. The sensitivity of SEF and ERC to the strength and radial location of low-level cooling is further investigated.
Professor Chen received his Ph.D in the Institute of Atmospheric Physics (IAP). After holding a position in IAP, he paid visits in several universities and research institutes around the world, such as City University of Hong Kong, National Taiwan University, and University of Tokyo, for Postdoc Fellow, Research Associate, and Visiting Professor. He is interested in the multi-scale tropical waves and their influence on tropical cyclones, tropical cyclone dynamics and simulation. He has published more than 60 articles in the top international journals as first author (e.g., Journal of Atmospheric Sciences; Journal of Climate; Monthly Weather Review). He is now a professor in IAP and also a member of typhoon discipline committee of Chinese Meteorological Society.http://www.escience.cn/people/chenguanghua/index.html