变点超阈法在增水重现期值计算中的应用

POT Method Based on Change-point Theory for Determining Extreme Surge Elevation

极端增水重现期值是制定海岸防护工程设计标准的重要依据之一。本文以香港鲗鱼涌站21年的实测数据为例,研究超阈法在极端增水重现期值计算中的应用。通过变点理论定量计算,结合超阈样本的年出现频次是否服从Poisson分布,和GP分布拟合情况综合确定阈值;用GP分布拟合超阈样本与频次分布结合,得到增水的P-GP复合分布。用该复合分布分析样本与传统年极值法比较,得到的增水重现期值结果接近。研究表明,超阈法能有效用于极端增水重现期值的计算,基于变点理论选择阈值在增水极值分析中是可行的。

Determining extreme surge elevation is one of the important bases for the design standard of coastal protection engineering.This paper takes 21 years of measured data from Quarry Bay Station in Hong Kong as an example and studies the application of the POT method in extreme surge elevation return period.Through the change-point method,the threshold is determined by combining whether the over threshold sample could fit the extreme value distribution well and whether the number of threshold exceeded each year meets the Poisson distribution.GP distribution is used to fit the over threshold samples.GP distribution and Poisson distribution are combined to derive P-GP multivariate distribution.The results of P-GP multivariate distribution approach that of traditional annual maximum method.The study shows that the POT method can be used to calculate the value of extreme surge elevation,and it is feasibility to select the threshold value based on change-point theory in extremum analysis of surge elevation.