Analysis Of Spatial-temporal Characteristics Of Waves And Prediction Of Significant Wave Height In The South China Sea

In recent years,global climate change is abnormal,wave disasters occur frequently,and with the development of the social economy,fossil energy is increasingly limited by the pressure of the peak of carbon emissions.It is of great strategic significance to carry out the comprehensive analysis and prediction of waves and the research on the development and utilization of wave energy to maintain people's property security and adjust China's energy structure.The South China Sea,the third-largest marginal sea globally,has a unique geographical location,complex seabed topography,rich marine resources,numerous islands,and is the central area of typhoon activities.Marine disasters occur frequently.It is close to Guangdong Province and Guangxi Province of China,with many coastal ports and developed fishery resources.It is of great significance for China's economic development to carry out a comprehensive study of the wave field in the South China Sea.Based on the reanalysis data set of the European Center for medium-range weather forecast,this paper analyzes the temporal and spatial variation characteristics of the wave field in the South China Sea from 1979 to 2020.Then,the wave power density in the South China Sea is calculated,and the availability of wave energy in the South China sea is analyzed.Secondly,the variation of the significant wave height(SWH)in the Beibu Gulf of the South China Sea from 1979 to 2018 and its influence mechanism are discussed.Finally,the prediction of the monthly SWH in the South China Sea is carried out based on the multiple sine function decomposition(MSFD)model.Firstly,through the Mann-Kendall test and regression analysis,it can be concluded that the wave mixing field and swell field in the South China Sea have an evident growth trend.The growth rates of SWH and significant height of total swell are0.18cm/a and 0.19cm/a,respectively,both of which began to grow around 1990 and reached a significant level.In the past 42 years,the growth of the mean period of total swell is the most powerful,the growth rate is 0.0082s/a.Besides,from the perspective of spatial distribution,the growth of wind wave mainly occurs in the northern part of the South China Sea,and the increase of swell mainly occurs in the southern part of the South China Sea.Based on the analysis of the spatial distribution of the climatic wave field in the South China Sea,it can be concluded that the maximum values of the mixing field and the swell field are located in the northeast of the South China Sea,and extend to the southwest of the South China Sea,and their intensity gradually decreases.The intensity of the wind wave field is smaller than the former two,and there is also a significant value area in the southeast of Vietnam.The wave direction is mainly west in the northern sea,south in the southern sea,and southwest in the central sea.In a year,the values of wave height and wave period are relatively large from October to December and from January to February.The wave direction is mainly southwest from October to December and from January to April,northeast from June to August,and wave direction conversion months are from May to September.Then,the reserves,availability,enrichment,and stability of wave energy in the South China Sea are analyzed.The results show that the wave energy in the South China Sea is mainly concentrated in the northeast of the South China Sea.The more southward the sea area extends,the lower the availability and the lower the wave energy reserves in the coastal region.In a year,the availability of wave energy is higher from January,October to December.Secondly,the growth of SWH in the Beibu Gulf is significantly increased,and the wind speed change is not apparent or even has a weak trend.Through further analysis of the frequency of gale generation in the northeast of the South China Sea,it is found that the growth of SWH in the Beibu Gulf is controlled by both local wind and invasion swell.The increase of the frequency of gale generation in the northern part of the South China Sea results in the increase of westward swell intensity,which in turn leads to the increase of SWH in the Beibu Gulf.Finally,based on the MSFD model,the monthly average SWH of the South China Sea is predicted.The results show that the MSFD model is suitable for the prediction of SWH in the South China Sea,and the mean square error of the prediction results is less than 0.2820.