Numerical Simulation Of The Hydrodynamic Process Of The Luzon Strait And Its Response To The Kuroshio Invasion Path

The Luzon Strait is the main channel connecting the South China Sea and the Western Pacific,and is also a major outlet in the Kuroshio movement path.It has a significant impact on the water,hot salt,momentum and energy exchange between the South China Sea and the Pacific.Exploring the hydrodynamic characteristics here is of great significance to social and economic activities such as marine ecology,ship transportation,and military activities.In this paper,the regional ocean numerical model(ROMS)is used to establish a three-dimensional numerical model of the ocean circulation in the South China Sea.Based on the daily average numerical simulation results from 2006 to 2018,the way the Kuroshio invaded the South China Sea near the Luzon Strait and the distribution characteristics of the ocean front are explored And the characteristics of water exchange within the Strait,and further analyzed the influence of the Kuroshio intrusion on the water flux and the distribution of the ocean front.Based on objective indicators,the path of Kuroshio's invasion of the South China Sea through the Luzon Strait is diagnosed.The main paths can be divided into three categories: flow sleeve,crossing,and branch.The statistical results show that the path of Kuroshio in the Luzon Strait is dominated by branches,followed by crossing and flowing sleeves.In terms of seasonal changes,the crossover path is predominant in summer,and the branch path is predominant in other seasons.The changes in the three paths of the Kuroshio are mainly related to monsoon,terrain and ENSO factors.The monsoon and terrain factors mainly control the seasonal change of the Kuroshio path,and ENSO has a modulation effect on the annual change of the Kuroshio path.Taking the 120.75°E section of the Luzon Strait as the research object,the characteristics of the spatiotemporal changes of the latitudinal flow and the vertical structure of water flux at the section are analyzed.The results show that the latitudinal flow at the cross section presents an obvious multi-nuclear structure,the flow pattern distribution changes little with the seasons,and the flow velocity change is greatly affected by the seasons.There are obvious seasonal and inter-month changes in the cross-section water flux;its vertical structure presents a "sandwich" structure in the annual average,spring,autumn and winter,and a "four-layer" structure in the summer half-year(May-September),And the thickness of each layer also changes with time.Using the canny edge diagnosis method to diagnose the sea surface temperature(SST)front near the Luzon Strait,the results show that the ocean front is likely to form in most areas of the Luzon Strait throughout the year,and the ocean front seasonal changes are obvious.Solar radiation,terrain,Kuroshio invasion and monsoon are the main factors for the generation and dissipation of ocean fronts in the region.Based on the various parameters of the ocean front,the autumn ocean front is the weakest,it is the front formation period,the winter is the mature period,and the spring and summer are the transition period.Finally,the daily data are used to screen the occurrence times of different paths of the Kuroshio,and the average water flux structure and distribution characteristics of the ocean front of the Luzon Strait under different paths are counted.The results show that the black tide flow path has the largest latitudinal flow velocity and the branch path has the largest water flux.When the Kuroshio crossing path occurs,the vertical structure of the Luzon Strait water flux is similar to the summer structure,that is,the "four-layer" structure appears,and the vertical value of the water flux of each layer of the branch path is the largest.The Kuroshio mainly affects the flux of shallow water in the surface layer(538m)of the Luzon Strait.The different paths of the Kuroshio have a great relationship with the generation and dissipation of the Kuroshio intrusion front.Among the three paths,the ocean front is the strongest under the Kuroshio branch path,and the weakest is the flow path.