A Study on the Extreme Wave Height Simulations by WAVEWATCH III

Abstract

During typhoon events accurate prediction of waves is essential to the ocean engineering design It can reduce the damage to coastal infrastructure and protect the safety of people's lives However due to the complex sea state and air-sea interaction it is still challenging to improve the prediction accuracy in the simulation of extreme typhoons In this study we will find out the appropriate solutions of the errors to improve the accuracy of extreme wave height calculation The WAVEWATCH III wave model (WW3) was used to calculate the wave in the past 9 typhoon cases which the maximum wave height is larger than 10 meters The source term packages and parameter settings from various countries (Taiwan France and USA) had been discussed to understand the ability of WW3 in these cases According to the comparison between WW3 results and buoy measured data it is shown that the three packages (ST2/4/6) of WW3 have good performance in the overall typhoon wave simulation However there is an underestimation in extreme wave height simulation in which the relative error 14% of ST6 simulation results is the smallest When using the settings suggested by the national operation unit the results of the overall wave height trend of typhoons show that the adjustment of the wind speed correction parameter (c0) in ST2 and the drag coefficient correction parameter (FAC) in ST6 has the most significant influence on the simulation of the extreme wave height during the typhoon For extreme wave high simulation the parameters adjust by United States Naval Research Laboratory in ST6 (this article is referred to as ST6_NRL3) have the best calculation results the relative error is 10% Furthermore the study also discusses the accuracy of wind field provided by WRF (The Weather Research and Forecasting) The average relative error of wind speed when the maximum wave height measured by WRF wind field and buoy is 26% It shows that the wind field accuracy has a greater impact on the extreme wave height simulation than adjusting WW3 parameters

Date of Award	2019
Original language	English
Supervisor	Dong-Jiing Doong (Supervisor)