Research On Numerical Simulation Of Waves In China's Offshore Waters By SWAN Model

Research on ocean wave is an important part of the ocean research.With the rapid development of computer science,the numerical simulation can accurately simulate the process of ocean dynamics and predict future ocean motion at this stage.It is not only a useful supplement to ocean experimental research,but also can be further applied to the experimental results.Therefore,in the field of marine research,the numerical simulation is more widely used.SWAN model is one of the third-generation wave numerical models commonly used at present,which is suitable for wave simulation in shallow water areas such as coasts,lakes and estuaries.Based on SWAN model,the wave in China's offshore waters especially in the Taiwan Strait is numerically simulated under different parameter settings and different wind field driving conditions,and the simulation results are analyzed in this paper.In this paper,the Taiwan Strait is taken as the research area,and CCMP wind field data is used as the wind field driver.Firstly,starting from the different physical processes of SWAN model itself,the simulation results of different parameter schemes for the same physical process are compared with the measured data of buoy,and the best SWAN model scheme in this paper is determined as follows: 1)the parameterization scheme of wind input exponential growth and energy dissipation of white crown fragmentation term: Janssen scheme;2)Calculation method of bottom friction dissipation: COLLINS calculation method;3)Nonlinear wave-wave interaction:three-wave nonlinear interaction;4)Wave breaking parameter value caused by shallowing: 0.73.Then,starting from the driving term of model wind field,the simulation results of CCMP wind field data,CERA-SAT wind field data,ASCAT wind field data and buoy wind field data are compared with measured data of buoy.It shows that the correlation coefficient between the simulation results of the four kinds of wind field data and the buoy data at the buoy point is above 0.93 with the highest 0.97,and the simulated wave height is smaller than the buoy wave height on the whole;the simulation results of CERA-SAT wind field data and buoy wind field data are the closest to the buoy measured data,while the simulation results of ASCAT wind field data are the most unsatisfactory.Then taking the CERA-SAT wind field data as the wind field input,the influence of the temporal resolution and spatial resolution of the wind field data on the accuracy of the simulation results is explored by changing the temporal resolution and spatial resolution of the same wind field data.The research shows that improving the temporal resolution and spatial resolution can improve the accuracy of the simulation results,but the improvement effect of the temporal and spatial resolution on the simulation results is weakened after reaching a certain accuracy,and the improvement of the temporal resolution is more obvious than the improvement of the spatial resolution on the accuracy of the simulation results.The conclusions above provide a reference for the SWAN model to simulate and forecast the waves in the Taiwan Strait.In view of the longest time coverage of CCMP wind field and the precision of its simulation results,CCMP wind field data is specially selected as the wind field input of SWAN model to simulate and analyze the seasonal variation characteristics of ocean waves in the Taiwan Strait.The results show that the ocean waves in the Taiwan Strait are mainly characterized by seasonal variation with larger wave heights in winter and smaller wave heights in summer,which is consistent with the measured results.This paper also takes the offshore waters of China including the Bohai Sea,the Yellow Sea,the East China Sea and the northern part of the South China Sea as the research area,and takes CCMP wind field data as the wind field input of SWAN model to simulate the waves in this large regional scale.The simulation results are compared with ERA-Interim reanalysis wave data.The research shows that the variation trend of SWAN simulation results in China's offshore waters is in good agreement with the actual wave variation trend.In the shallow waters closer to the coastline,the simulation results are closer to ERA-Interim reanalysis wave data.When the wave height is larger,the overall simulation results are better,while when the wave height is smaller,the error between the simulation results and the reference wave data is larger.Finally,the seasonal variation characteristics of ocean waves in China's offshore waters are also explored.The result shows that the ocean waves in China's offshore waters also show seasonal variation characteristics of higher wave heights in winter and lower wave heights in summer.