The Propagation Characteristics Of Rossby Wave In The North Pacific And Its Impact On The Kuroshio East Of Taiwan

Kuroshio is a very important western boundary current in the Northwest Pacific and plays an important role in the oceanic ocean thermal transport and climate change in the North Pacific.The Kuroshio east of Taiwan is the source of the Kuroshio in the East China Sea.The low frequency variation of the Kuroshio volume transport(KVT)will directly affect the SST anomaly in the Kuroshio watershed and affect the atmospheric circulation and precipitation in China.A large number of studies have pointed out that the variation of KVT in the east of Taiwan is mainly caused by the interaction of Kuroshio and Rossby waves,which spread from the ocean to the east of Taiwan.So,the study of Rossby waves propagtion charateristics,how they interact with Kuroshio,how they influence the curvature and shape of the Kuroshio path,and whether the oceanic water mass carried by the solitary Rossby waves can pass through the Kuroshio into the South China Sea and the East China Sea have important theoretical and practical significance.Based on the AVISO and SODA data,the propagation characteristics of Rossby waves in the North Pacific are analyzed,and some observational phenomena which can not be explained by the linear Rossby wave theory are proposed in combination with the previous research results.By means of theoretical analysis and numerical simulation,the influence of background flow shear and nonlinearity on the propagation of Rossby waves are discussed in the framework of nonlinear theory,which explains the observations in the ocean that can not be explained by linear Rossby wave theory.The main conclusions are as follows:· In the nonlinear Rossby wave theory,background flow shear,buoyancy frequency and ? effect are important factors for the existence of solitary Rossby waves.Solitary Rossby waves are non-dispersive waves,and the wave width is inversely related to the flow shear strength;the phase speed of solitary Rossby waves is greater than the linear Rossby waves;the phase speed is positively correlated with the amplitude and flow shear strength,and the greater the flow shear is,the more significant the effect of amplitude on the phase speed.· The phase speed of Rossby waves is faster in low latitude than in high latitude.Dissipation reduces Rossby waves intensity,propagation velocity,total energy and quasi-energy.· For flow shear ? < 0,cyclonic solitary Rossby waves exist and their meridional structure tilts northward;for flow shear ? > 0,anticyclonic solitary Rossby waves exist and their meridional structure tilts southward;· Solitary waves have the nature of transporting water mass,and the range of water transport is not north–south symmetry.The anticyclonic solitary Rossby waves favor the transport of the southern water mass,and the cyclonic solitary Rossby waves favor the transport of the northern water mass.Furthermore,by using the stratified fluid quasi-geostrophic theory,the high-resolution numerical experiments of the interaction between the first mode baroclinic Rossby waves and the Kuroshio are designed.The propagation characteristics of different types of eddies,three–dimensional structural variation of the interaction between the eddy and the Kuroshio in the East of Taiwan,and the flow distribution characteristics of water mass carried by eddies in the East of Taiwan are discussed in detail.The main conclusions are as follows:· The anticyclone eddy and the cyclonic eddy are propagated westward at the first baroclinic mode Rossby wave velocity under the influence of ? effect,in which the anticyclonic eddy is shifted southward during the westward propagation process,the cyclonic eddy is shifted northward during the westward propagation process.The depth influenced by eddy is about 2000 meters.· After the eddy reaches the waters east of Taiwan,the spatial structure of Kuroshio is changed by the interaction of eddy and Kuroshio,which makes a significant KVT fluctuations.The eddy and Kuroshio interaction time lasts about 100 days.· During the interaction of anticyclonic eddy and Kuroshio,anticyclonic eddy can not cross the Kuroshio to reach the west side of the Kuroshio,but along the east side of the Kuroshio flow to the north.When anticyclonic eddy reaching K1?K2section,the Kuroshio spindle in K1?K2 section first offshore then onshore,while causing the KVT in K1(K2)section decreases first(increases)and then increases(decreases).· During the interaction of cyclonic eddy and Kuroshio,cyclone eddy can be involved to the west side of the Kuroshio,then flow to the north along west side of the Kuroshio,while causing large offshore Kuroshio meandering and low(high)KVT in K1(K2)section.· When the oceanic water mass carried by anticyclone eddies reach the waters east of Taiwan,the upper 600 meters water mass flow into East China Sea under the influence of Kuroshio,and the water mass below 600 meters continue to spread westward through the bottom of the Kuroshio and Luzon Strait into the South China Sea due to the weak influence of Kuroshio.· When the oceanic water mass carried by cyclone eddies reach the waters east of Taiwan,the water mass can go through the Kuroshio to the west side of the Kuroshio,and then flow northward under the influence of the Kuroshio.The upper 300 meters water mass can flow over the Ilan Ridge to reach the East China Sea shelf;the water mass between 300–600 meters flow northwestward along the north coast of Taiwan after passing the Ilan Ridge,which can not reach the East China Sea shelf;the water mass below 600 meters can not flow over Ilan Ridge due to the topographic influence,but flow to the east of Ryukyu Islands waters before reaching the Ilan Ridge.