Research On The Comparison Of Statistic And Analytic Methods Of Extreme Wave Heights

Ocean wave is a fluctuant phenomenon occurred on the water surface. It contains enormous energy, while usually composes severe threaten. In the coastal and ocean engineering, the designed wave heights should be considered. At the same time, the statistic research on storm wave heights is very important in the fields of calculations of storm surges, the erosion of coast and sand beach.The thesis studies the estimation of designed wave heights, includes the long term and short term situations, with using the best sampling method, distribution function, method of estimation of parameters, then concludes the compounding scheme between them. In addition, it discusses how to deal with the data for better accuracy of the result, when it only has the data collected of every six hours in our country. This thesis also analysis the difference of observed data between every six hours and every hour, then amends the results of the every six hours. The main conclusions are as follows:(1) When study the data of long-term which is collected off Sydney in Tasman Sea, the Annual N-Largest method is the best one, secondly, the Peak-Over-Threshold method, and thirdly, the Annual Maximum method. When using N-Largest method, N=5 or N=6 is better. It also finds that the POT method is insensitive to the threshold when the average number of storm peak wave heights per year, λ, 8 to 10. When using distribution function, we should firstly choose the three parameters of Weibull distribution function, then the Gumbel distribution function, and using the method of estimate the parameters, choose the least-square fitting method.(2) It brings forward a new method to estimate the parameters of three parameters of Weibull distribution function. The new method gets the formula of shape parameter, from the extreme theory, then gets the result from trial.According to the method, the solution process becomes simple and feasible, also the result becomes more accurate.(3) The study analysis the data collected from Lianyungang station of China. It finds that it is more stable to use the sample of month extreme wave heights than POT method. The best compounding scheme for this station is using sampling method of...