The Roles Of The Spatial Structure Of The Initial Perturbations In The Variation Of The Kuroshio Path South Of Japan And Its Nredictability

We use barotropic inflow-outflow model to study the roles of the spatiallocations and patterns of the initial perturbations in the variation of the Kuroshio path.The research includes two aspects:First, we study the mechanism of the initial perturbations affecting the Kuroshiopath. Setting the non-large meander path equilibrium as reference state, we calculatethe CNOP initial perturbation. We superimpose the CNOP initial perturbation to thereference state, study its development process and compare it with the developmentprocess of random perturbation. We find that the CNOP initial perturbation canchange the non-large meander path into large meander path while the randomperturbation cannot. In this sense, the CNOP initial perturbation may be treated as theoptimal precursor of the Kuroshio large meander path. The further analysis indicates:1. The process of the CNOP initial perturbation changing the Kuroshio path into largemeander path is that a cyclonic eddy transports to the downstream and grows up there.2. The nonlinear effect transports the cyclonic eddy to the downstream. In anotherword, the advection transports the eddy.3. The eddies in the CNOP initialperturbation case and random perturbation case will both transport to the downstream,but the CNOP case eddy can grow up and change the Kuroshio path into largemeander path while the random perturbation case eddy cannot. We find that thenonlinear effect strengthens the cyclonic eddy in the CNOP case while the nonlineareffect weakens the cyclonic eddy in the random perturbation case. So the nonlineareffect is very important in the process of the Kuroshio large meander path formation.4. The bottom friction is unimportant in the Kuroshio path variation.Then, we study the roles of the position and the pattern of the initial perturbationsin the variation of the Kuroshio path. We select21areas, including the CNOPsensitive area. We superimpose the CNOP and random initial perturbations to the21areas and calculate their objective function value. We conclude:1. Superimposing theCNOP initial perturbation to the CNOP sensitive area has the largest objectivefunction value.2. The objective function has larger value when the random initialperturbations are superimposed to the CNOP sensitive area than other areas.3. Inmost areas, the objective function which is resulted by CNOP initial perturbation has larger value than random perturbations.4. Among random initial perturbationssuperimposed to the CNOP sensitive area, the ones which are similar to the CNOPinitial perturbation have larger objective function value. In summary, the perturbationin CNOP sensitive area is more important than in other areas in the variation of theKuroshio path, and the CNOP initial perturbation is more likely to change theKuroshio path into large meander path.