臺北港風與波浪關連性之統計特性研究

Abstract

目前以方程式建構的數值模式或經驗公式推算波浪可能產生之誤差，其原因部分來自於給定的風速與實際值有差異，因為波浪模式所用的風速為海面上10m之風速。此海面10m風速值在台灣上少有實測資料，而改引用陸上或高空衛星觀測值來取代。交通部運輸研究所港灣技術研究中心已在台北港外海設置一個觀測樁，同時測量波浪與風速，波浪以觀測樁水下-5m及-10m處各安裝無線電傳輸之潮波流儀來觀測，在觀測樁之海面上10m處有自記式之風速儀。本計畫主要探討同時觀測風速及波浪資料的統計特性，並建立兩者間之關係。 本計畫將透過波浪的長期資料進行基本統計與波譜分析，以瞭解不同時間下的各種統計特性，探討臺北港在各月份及季節波譜特性之參數，以提供未來分析波浪特性與工程實務應用之參考。本計畫同時考量海面風速強度、風向與持續性進行風浪相關性分析，並以風速、風向分布及風的持續性建立波浪波高及週期的關係。

Accuracy of wave models or empirical formula for forecasting waves is related to wind velocity at 10m high above seas which is a dominant input source. Observed data of wind velocity at 10m high above seas is commonly unavailable in Taiwan so that wind velocities at land location or from satellite information are alternatives instead of wind velocities at 10m high above seas. A field observation particular designed for simultaneously measuring waves and winds at Taipei offshore seas was set up by Harbor and Marine Technology Center. Two ADCPs below 5 and 10m from mean sea level are used to measure waves and currents and automatic-record anemometer is used to observe wind speed and wind direction at 10m high above seas. The project is to investigate the statistic properties of the useful simultaneous wind and wave hourly data for years and to establish their relationship that can be used to have fast forecasting waves from winds. Wave statistics are applied to study the monthly and seasonal statistics. Spectral analysis is used to evaluate the best fitting spectrum for waves at Taipei waters. Valid parameters in the fitted spectrum for monthly and seasonal waves are obtained for future engineering application. Angular distribution of wind velocity for Taipei local winds will be examined from some suggested distributions. Persistence of wind velocity is a key to continuously generating waves. Thus wind persistence is a special issue in this project. Empirical formula of wave height and period will be proposed to relate with wind speed, direction and persistence.