Application of Poisson Gumbel Distribution to Wind Speed Calculation for the Southeast Coastland of China

Tropical cyclone (TC) is the main cause of extreme wind in China southeast coastal, especially in coast to the south of the Yangtze River delta. The TC maximum wind speed may exceed 40 m·s^-1, raising the risks for engineering design near the coast. The 1961—2006 TC/typhoon almanacs published by Shanghai Typhoon Institute and wind data of ground stations are investigated, and the TCs that pass within 3 latitudes away from the coast are defined as influential ones. There are 428 TCs passing through this area from 1961 to 2006. Typhoons and strong tropical storms are major TCs with the percentage up to 33.6% and 25.7%, and 59.3% in total. Super strong tropical cyclones and strong tropical cyclones often cause losses to wind farm, and the percentage of them is 7.9% and 13.6%， respectively. The percentage of tropical storm and cyclone is 10.3% and 8.9%, and these TCs usually bring lots of power for coastal wind farms. The numbers, motion paths and intensity of TCs generated from Northwest Pacific Ocean are stochastic every year. Therefore, the number of influential tropical cyclones make some kind of discrete distribution in China southeast coast, obeying the Poisson distribution. But maximum wind speed under the influential tropical cyclones (TC) may satisfy some kind of continual distribution, obeying the Gumbel distribution. Based on the Poisson Gumbel compound extreme distribution, the extreme wind speeds of different time scales can be obtained using TC data of coastal weather stations for the period of 1961—2006. The result indicates that the Poisson Gumbel joint distributing algorithm is superior and gives stable and accurate results when the observed data sample sequence is short, especially for the strong weather event like TC which is very random. For 53.9% of the stations, the extreme wind speed of 50 years is less than 50 m·s^-1. The extreme wind speed of 50 years exceeds 42.5 m·s^-1 in Dacheng, Shengshan, Shanmen, Nanjishan Islands of Zhejiang Province, Beijiao coast and Taishan Island of Fujian Province, Zhelang and Shangchuan Island of Guangdong Province, and Xisha Island of Hainan Province. In these areas, the risks of tropical cyclone for wind farms construction should be paid enough attention.