Tropical Cyclone Induced Storm Wave Hazard Assessment In Hainan Island,China

Tropical cyclones are the most serious type of meteorological disaster that have had a great effect on Hainan Island in recent decades.With the rapid expansion of the deep sea net cage scale in the nearshore area of Hainan Island,the need for tropical cyclone-induced storm wave hazard assessment and refined storm wave forecasting are urgently needed.To solve those problems,this dissertation mainly studied the characteristics of storm wave behavior in certain deep sea net cage area,established a refined storm wave forecasting system for the coastal areas of Hainan Island and a wave hazard comparison and assessment method for different sea areas.In the present dissertation,the wind-wave-current coupled model ADCIRC+SWAN(Advanced circulation model,Simulating Waves Nearshore),which considers the effects of tidal and storm surges,was used to hindcast historical tropical cyclone events.Comparisons made between observations and simulated results during typhoon Rammasun(2014)indicate agreement.Storm wave were simulated in Houshui Bay on the basis of a large set of historical tropical cyclones in the North-West Pacific Basin between 1985 and 2015 to obtain the storm wave level maps.The results were used for the statistical analysis of the maximum significant wave heights in Houshui Bay associated with local wind velocity,distance from cyclone center and cyclone track.In addition,results demonstrate that the cyclone tracks passing through the northeast corner of Hainan Island into Beibu Gulf caused the most hazardous wave heights in Houshui Bay.Two groups of synthetic typhoon tracks were designed to further investigate the worst case of typhoon scenarios.Based on the wave-current coupled model,this study established a storm wave forecasting system for the coastal aquaculture areas of Hainan Island.This system adopted an unstructured grid with a high resolution and a nearshore resolution up to100 m.Storm waves were hindcasted during the No.9 typhoon RAMMASUN in 2014 for the coastal aquaculture areas of Hainan Island.Results obtained were in agreement with the measured data.Additionally,the accuracy of the storm wave forecast for a tropical storm process in July 2018 was examined by using forecasted winds at the height of 10 m above mean sea level and pressure data from the GFS(Global Forecast System).Average relative errors of 48 h and 24 h significant wave heights' forecast were 20.75% and 17.0%,respectively.Overall,forecasting accuracy was within acceptable range and this system could satisfy the storm wave forecasting demands of the coastal aquaculture area.In the present dissertation,the ADCIRC+SWAN model was used to simulate tropical cyclone events in the last 30 years.Compared simulated results and observations during typhoons JEBI(2013),HAIYAN(2013)and KALMAEGI(2014)were in agreement.This study statistically analyzed maximum significant wave heights on the basis of a large set of simulated storm wave level maps to derive the wave heights of different return periods.Then,the results of nearshore wave hazard classification were obtained by applying the Affinity Propagation(AP)clustering method to dozens of nearshore profiles.The results demonstrate that the risk at any point in the nearshore area of Hainan Island is dominated by the wave hazard type and water depth condition.The wave hazard assessment method developed for Hainan Island will be significant in assisting government decision-making in the rational planning of deep sea net-cage aquaculture.