The influence of Tropical cyclone structure on storm evolution and its interaction with topography

Due to the lack of observations available around tropical cyclones (TCs), the structure of TC is generally not well represented. It is well known that the size of TC could affect the strength of beta gyres, owing to planetary vorticity advection by the storm's cyclonic circulation, and thus affecting storm motion (Holland 1983). The study from Jiang and Wu (2008) showed that the structure of TC would affect the track deflection when TC approaches high mountain topography.

In this study, a series of numerical simulations are conducted using the advanced research version of the Weather Research and Forecasting model (V3.0.1) to examine the impact of TC structure on the track, intensity and its interaction with topography. Different TC structures are prescribed by applying different values of the structure parameter. Four real-case simulations are conducted for typhoons making landfall in Taiwan. Examination of the beta gyres showed that TCs with more compact structure tend to experience more northward track deflection. Regarding the track deflection by topography, it is found that TCs with more compact structure interacted would experience less topographically-induced track deflection. It is of interest to note that because there is stronger track deflection for less compact TCs, this may increase the duration of the storm passage. This result implicates the importance of TC structure in affecting the TC-terrain interaction process, and suggests the importance of observations in improving the analyses of TC structure before they approach the high-terrain island(s).