The Analysis Of Typhoon Extreme Wind In China Offshore And The Numerical Simulation Of Typhoon 'Fung-wong'

The offshore area near China is a region frequently affected by tropical cyclones (TC). For sake of affection from TC, the ocean engineering is often destroyed, so the extreme wind of TC is one of important parameters for the design of ocean engineering. Wind field distribution of offshore TC is asymmetrical, therefore, the asymmetrical typhoon model is adopt to calculate the 2-hourly wind field of TC which affected China offshore from 1961 to 2007 with the resolution of 50km×50km, combining with TC central pressure and max wind speed data (1961-2007) of CMA, England Hadley Center reanalysis data (1870-2003) and reanalysis data of Japan Meteorological Agency (1978-2007). And then, automatic weather observing station data is used to compare with the calculating results. The TC extreme wind speed of 20, 30, 50, 100 years return period of each grid is calculated respectively by using with the Poisson-Gumbel joint extreme value modal and Weibull model.Taiwan channel is one of the regions with frequent TC activity and TC is severe before it landfall on Taiwan island. But through the analysis of the TC extreme wind value, we find that the extreme wind speed caused by TC is less in the middle-southern sea area of Fujian than adjacent sea areas because Taiwan Island changes the track and intensity of TC. In order to analyze and explain that how the Taiwan island affects the intensity of TC and the capability of numerical model to simulate the track and intensity of TC which pass through the sea area, we simulated'Fung-wong'(0808) by using the mid-scale model WRF through four different planet boundary scheme (MYJ, YSU, MRF and none planet boundary scheme) under real terrain and terrain sensitive test (0%, 50%, 100%, 200% of the real terrain elevation) with MYJ scheme.Through the analysis of TC extreme wind and simulation, the main results were gotten as following:(1) The asymmetrical typhoon model used in this thesis is easy to calculate the wind field of typhoon, and the character of the wind field in accords with the asymmetrical character of real wind field;(2) The characters of the TC extreme wind of N years return period in China offshore region is that the extreme value is increase by degree from north to south in China east sea and yellow sea; and it's increase by degree from west to east in Beibu Gulf, north of China south sea and eastern of Bashi channel;(3) In the sea area near the coast, the TC extreme wind is highest from middle- southern sea area of Zhejiang to the northern sea area of Fujian, the next is eastern sea area of Hainan, in middle-southern sea area of Fujian the extreme value is less than its adjacent sea area and it is least in the north of Hangzhou Gulf and Beibu Gulf;(4) MYJ scheme is better than other schemes for the intensity change of TC, the track and the landfall position are all similar to the real situation;(5) It is about 3 hours earlier than the time of landfall, that'Fung-wong'begins to decrease for the effect of Taiwan island, and the higher terrain elevation of Taiwan island is , the stronger the intensity change of'Fung-wong'is; and the Taiwan island can makes the track of'Fung-wong'change, the higher the terrain is, the earlier the time of the track change of'Fung-wong'is;(6) The dynamical and the heat field of'Fung-wong'parent asymmetrical for the Taiwan Island, and the higher the terrain is, the stronger the asymmetry is. The position of maximum latent heat release changes for the Taiwan island, from the middle-high level of troposphere to the low level of it, so the structure of warm center is destroyed, and that will affect the intensity of TC;(7) The Taiwan Island is easy to cause the sub-circulation, and the higher the terrain is, the strong the sub-circulation is. The sub-circulation joins in the axis symmetrical circulation of'Fung-wong', which can influence the structure and the intensity of'Fung-wong'.