Polygonal Eyewall and Mesovortices Structure in a Numerically Simulated Typhoon Rusa

In this study, to elucidate the inner structure of Typhoon Rusa (2002), a numerical simulation was conducted using a two-way triple-nested cloud-resolving nonhydrostatic model with a 2 km horizontal grid size on the finest nested mesh. The model successfully reproduced the features of polygonal eyewall structure observed in Typhoon Rusa. The simulated asymmetric structure in the inner-core region was dominated by a number of mesovortices within or near the eyewall in the lower and middle troposphere. Meso-lows on the horizontal scale of 20-30 km were found at the kinks of polygonal eyewall, and between them meso-highs existed. The modification of radial flow by the mesovortices affected not only the location of eyewall, but also the convective activities in the eyewall by causing the interaction between the eye and the eyewall. The horizontal distribution of the potential vorticity (PV) showed the wave-like pattern related to the mesovortices near the eyewall, which was quite similar to the ideal numerical experiments of Schubert et al. (1999) and Kossin and Schubert (2001).