The Dynamic Mechanism Of The Luzon Strait, The Kuroshio Variation

The academia pays much attention to the transition and dynamic mechanism of the Kuroshio at Luzon Strait, and it plays an important role in determining the whole balance of mass and energy of the South China Sea. Chapter one gives a summary of the SCS and Kuroshio at Luzon Strait, and hysteresis in oceanography. Both the transport and non-dimension parameterγ(ratio of the half width of the gap and width of Munk boundary layer) control the formation of the Western Boundary Current at the gap (Chapter two). In Chapter three, we analysis how the meridional winds change the formation of the WBC at the gap, including typhoon cases. At last chapter, when the WBC is at its critical phase to transfer to another phase, meso-scale eddies may also disturb the formation the WBC. And These results can be used to explain some feature of the Kuroshio at Luzon Strait.Considering the width of the gap, viscosity coefficient and transport of the WBC, the model results shows whenγ≤3.05, no matter how small of the transport, the WBC can not penetrate into the gap. When 3. 05<γ<4.42, the WBC can penetrate when the transport is small, while the WBC leaps when the transport is large, and one certain transport is corresponding to one certain feature. Whenγ≥4.42, the WBC may be in one of the two regime(penetrating state or leaping state)for the same parameter, depending on its initial state. The bifurcation graph of the formation of the WBC versus the parameters (γand transport) is revealed.The path of the WBC is mostly determined by the transport of the flow, winds and eddies may also affect the transport. We focus on the effects of meridional winds influence the transport without changing the curl of the wind. The results illustrate that northerly wind favor anti-cyclonic intrusions of the WBC into the gap whereas southerly winds favor leaping across the gap. The Ekman transport which induced by northerly winds in the gap do not change the path of WBC evidently. But the blocking of Ekman transport at south of the gap can reduce the transport of the WBC remarkably, which results in penetrating state. The path of the WBC is difficult to change when it is beyond the critical value of the transitions.Meso-scale eddies may also change the transport of the WBC. When the WBC is at critical state, the perturbation of eddies may change the state evidently. When the WBC is at critical value of penetrating state, cyclonic and anti-cyclonic eddy at right side of the gap both may change it to leap. When the WBC is at critical value of leaping state, neither cyclonic or anti-cyclonic eddy at right side of the gap can not change it to penetrate. Experiments also reveal the position of eddies is quite important, the south position of the gap is much more important than the north.