Estimating the Parent Distribution of Storm Type-Separated Annual Maximum Wave Height on the Northwestern Pacific Ocean

本研究通过对西北太平洋包括日本海和东中国海的20000多年台风或10000多年低压系统产生的海浪进行蒙特卡罗模拟，产生了一个大范围的风暴类型分离的年最大波高数据样本，并基于极值分析估计了每个AM波高数据集的母分布。此外，通过与过去50年历史台风和过去20年历史低点的返回波高度及其比率的类似评估的比较，研究了可用性。主要结果如下：1.50年回波波高的分布与各类历史暴雨的估计值在定性和定量上是一致的。2.台风AM资料的母分布近似为威布尔分布，形状参数由西南地区的4左右下降到西北地区和东北地区的1.4左右。在日本海，形状参数从日本一侧向大陆方向递减。对于低产AM资料，形状参数从东部地区的2开始呈半圆形递减，在日本周边大范围内采用冈贝尔分布。3.无暴雨型AM资料的母体分布受主要的风暴分离AM资料的影响较大。4.R年回波波高的样本高度近似为威布尔分布，且重现期与样本量之比越大，形状参数的值越小。这意味着随着比率的增加，样本分布的拖尾时间会更长。

This study produces a large size sample of storm type-separated annual maximum(AM) wave height data through a Monte-Carlo simulation of typhoon-generated waves over 20,000 years or low pressure system(low)-generated waves over 10,000 years on the Northwestern Pacific Ocean including the Japan Sea and the East China Sea, and estimates a parent distribution based on the extreme value analysis for each of the AM wave height data sets. Also, the availability is investigated through the comparison with the return wave heights and their ratios similarly evaluated for historical typhoons in the past 50 years and for historical lows in the past 20 years. Main results are summarized as follows.1.The distribution of 50-year return wave height is in qualitative and quantitative agreement with that estimated for each type of the historical storms.2.The parent distribution of typhoon-generated AM data is approximated with the Weibull distribution, in which the shape parameter tends to decrease from around 4 on the southwestern area toward around 1.4 on the northwestern area and on the northeastern area. On the Japan Sea, the shape parameter decreases from Japan side toward the continent. For the case of low-generated AM data, the shape parameter decreases semi-circularly from a value of 2 on the eastern area, and the Gumbel distribution is selected on the wide area around Japan.3.The parent distribution of storm type-free AM data is strongly affected by predominant storm-separated AM data.4.A sample of R-year return wave height is highly approximated with the Weibull distribution, and the greater the ratio of return period to sample size is, the smaller the value of shape parameter becomes. This means a longer tailing of the sample distribution with increase of the ratio.