Estimation of Typhoon-Generated Extreme Storm Surges and Waves on the Western Seto Inland Sea and their Real-Time Forecast

本文利用51年历史台风和500年模拟台风的预报结果，对西户内海9918和9119台风期间的海岸灾害和海况进行了研究，并对相关海域的风暴潮和波浪极值进行了估计。此外，还尝试对台风产生的风暴潮和风浪进行实时预报。主要研究结果总结如下：台风9918和台风9119在西濑户内海沿岸地区造成了严重的破坏，但受损地区不同，取决于与天文潮汐和风暴潮相关的海平面。利用每小时的气压、风和海平面进行空间插值，可以跟踪它们在与台风运动有关的海域上的时空变化。台风9918可能在西濑户内海西部的索那达海域带来了超过50年来最大海浪的极高海浪。从福冈到山口县的沿海地区，高水位阶段附近的高浪和风暴潮叠加是造成严重灾害的主要原因。50年回归风暴潮高度从本哥海峡向内海区域和内海西部和东部区域增加。50年回归波高从本古海峡12 m到内海6 m，向内海西部和东部海域减小。模拟台风的回归值与历史台风的回归值基本一致。台风、风暴潮和海浪的实时预报系统可以对它们的时间变化作出合理的估计。

This study investigates coastal disasters and sea state conditions during Typhoons 9918 and 9119 on the Western Seto Inland Sea, based on the data analysis and estimates extremes of storm surges and waves on the concerned sea area using hindcast results for historical typhoons over 51 years and for simulated typhoons over 500 years. Also, a real time forecasting for typhoon-generated storm surges and waves is attempted. Main results are summarized as follows.1. Typhoon 9918 gave severe damages along coastal areas on the Western Seto Inland Sea as well as Typhoon 9119, but damaged areas are different from each other, depending on sea levels associated with astronomical tides and storm surges.2. Spatial interpolations with use of one-hourly atmospheric pressure, winds and sea levels make it possible to follow their space-time variations on the sea area associated with movement of the typhoon.3. Typhoon 9918 may have brought about extremely high waves exceeding the maximum waves in the past 50 years on the Suounada sea area, western part of the Western Seto Inland Sea. Superposition of high waves and storm surges near the phase of the high water level ia a main cause of severe disasters along the coastal areas from Fukuoka to Yamaguchi Prefectures.4. 50-year return storm surge height increases toward the inland sea area from Bungo Channel and toward the western and eastern areas on the inland sea. Also, 50-year return wave height changes from 12 m on Bungo Channel to 6 m on the inland sea and decreases toward the western and eastern sea areas on the inland sea. The return values evaluated for simulated typhoon cases are in reasonable agreement with those for historical typhoon cases.5. A real time forecasting system of typhoon-generated, storm surges and waves yields reasonable estimates for their time variations.