Study On The Characteristics And Influence Mechanism Of The Three-dimensional Structural Changes Of The Kuroshio Front In The East China Sea

In this paper,combined with sea surface temperature,salinity,chlorophyll concentration,and diffuse reflectance data,the seasonal variation characteristics of the surface Kuroshio front are studied,and the three-dimensional structure of the Kuroshio front in the East China Sea from the surface to the bottom layer is studied by three-dimensional reanalysis of temperature and salinity data.Characteristics,the influence of monsoon and Kuroshio on the surface Kuroshio front is also discussed through the sensitivity experiment of monsoon and Kuroshio.The Kuroshio sea surface temperature front in the East China Sea is stronger in winter and spring,followed by autumn,and disappears in summer.The change is manifested by the increase in temperature fronts from January to March,and the strongest fronts in the year from March to March,5-7.The monthly temperature front decreases,July-September is the weakest,and September-December the temperature front strengthens again;the surface salinity front is the strongest in summer,followed by spring and autumn,and disappears in winter.The change is manifested as the salt in January The salinity front is similar and the weakest throughout the year.The salinity front from March to June shows an increasing trend.The salinity front from June to October is similar and the strongest throughout the year.The salinity front weakens from October to December;the chlorophyll at the surface Kuroshio The front change is mainly whether the front area is clear and obvious,which is the most clear in summer,the late spring and early autumn are similar,and the winter front area is the most chaotic;the main change of the diffuse attenuation coefficient front is also whether the front area is clear and obvious at the Kuroshio.It is clearest in summer,similar in spring and autumn,and the frontal zone is the most chaotic in winter.The long-term average sea surface temperature front area is mainly in the 70-200 m water depth area.The center line of the temperature front is roughly parallel to the stream axis of the Kuroshio.There is a northward branch in the middle of the Kuroshio to the south of Jeju Island.Due to the combined influence of the Taiwan warm current,the Kuroshio and its branches,the Kuroshio temperature front in the East China Sea always exists from the sea surface to the seabed in winter and spring in the area shallower than 200 m,and mainly appears in the water layer below 50 m in the summer and autumn.The temperature front gradient of the Kuroshio islarger in the depth of 100-500 m,and even the gradient value is greater than the gradient value at the sea surface above the same position,and the gradient decreases in the lower layer.The three-dimensional salinity front shows that the surface salinity front area in summer and autumn always exists in the 0-200 m water depth area,and the center line of the temperature front is roughly parallel to the stream axis of the Kuroshio,in the middle of the Kuroshio south of Jeju Island.There is a branch to the north.In winter and spring,the salinity front mainly ranges from 150-200 m,and the salinity front continues to strengthen below 200 m water depth.The strongest salinity front appears at a water depth of 300 m and its intensity is higher than that of the surface salinity front.The salinity front at a water depth of 150-400 m exists almost throughout the year.The Kuroshio has obvious regional changes,but the flow velocity is generally the smallest in January-March.The position of the Kuroshio front in the northeastern section of Taiwan Island has the largest change and the change in current spread is relatively large.The position of the Kuroshio at the PN section has the smallest change and basically remains unchanged.The position of the northern part of the tide varies slightly but the current spread changes significantly,and the current spread is the widest in autumn.Affected by the path,width,depth,and velocity of the Kuroshio,the influence of the Kuroshio temperature front in the East China Sea on the shelf area has both regional and seasonal differences,and is generally greater than the depth of arrival of the Kuroshio at 0.2m/s.The depth is about 200 m,and the deepest can affect the water depth of about 1000 m.And through the ROMS sensitivity experiment,it is found that the summer monsoon is not the main factor affecting the surface Kuroshio front at that time,but the increase of the flow can enhance the temperature front and salinity front of the Kuroshio current.