A-244 エネルギー時系列データから推測される 2 層風成海洋循環のカオスへの道筋

概要

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A numerical study is made of a two-layer quasigeostrophic model for a wind-driven subtropical gyre in a square β-plane basin bounded by no-slip walls. We analyze the time series of basin-averaged potential and kinetic energies to examine changes in dynamical regimes when the strength of the steady winds is gradually increased while the horizontal eddy viscosity coefficient is fixed. We have confirmed distinct transitions from steady states to aperiodic states, including both period-doubling and inverse period-doubling bifurcations. After the occurrence of quasiperiodic states associated with interannual variability, we have detected three successive period-doubling bifurcations, leading to the spectral broadening. Therefore, in contrast with previous works in which the horizontal eddy viscosity coefficient is decreased, a Feigenbaum scenario is very likely to exist and may be responsible for the decadal variability in the present model.
日本流体力学会の論文
2003-07-28