The influence of Tropical cyclone structure on eyewall evolution simulation of Typhoon Sinlaku (2008) crossing Taiwan

Typhoon Sinlaku (2008) had the most observational data which conducted by the T-PARC field campaign and it reintensified after passing Taiwan. There are many scientific issues associated with it which could be further studied. These are: 1) the existence of hot tower during development stage; 2) the phenomena of concentric eyewall; 3) the contraction of eyewall before landfall; 4) the looping track during landfall; 5) the eyewall breakdown after landfall in Taiwan and reformation before landfall in Japan. In this study, a series of numerical simulations are conducted using the advanced research version of the Weather Research and Forecasting model (V3.2) to examine the impact of different terrain conditions and vortex structures on the eyewall evolution when Sinlaku crossing Taiwan. According to best track analysis, Sinlaku approached Taiwan from southeast then turned toward northeast after landfall. This recurvature track can be well simulated in all of the experiments. Regarding to the intensity simulation, though the intensity is much weaker than observed value at the initial time in the experiment without the implanted bogused vortex, the intensity increases quickly and closes to observed value after 48 hours simulation. For the simulation results in the experiment with the implanted bogused vortex as well as full terrain, the eyewall evolutions are well simulated, i.e., the eyewall contract before landfall, break down over land, and reorganize after landfall. However, the eyewall maintain well structure during the entire simulation period in both the without terrain and flat terrain with 1-m height experiment. These results indicate that the reorganization of the eyewall could not be simulated in these two experiments. On the other hand, through the sensitivity experiments of different vortex structure, it is shown that the storm with larger strength or eyewall radius tends to induce stronger wind and rainfall at the outer part of storm when it crossing terrain. This result indicates that the vortex contained larger angular momentum is much favorable to reform a new eyewall from the contraction of the outer rainband after it was affected by terrain. Based on these sensitivity experiments, it is suggested that the topography and the structure of the tropical cyclone play important roles for trigger and modulation the unique eyewall evolution which induced for the tropical cyclone passing the island.