赤道两层海洋模式中基本流的切变不稳定性

设计了一个热带赤道β-平面的两层海洋模式,在准长波近似下,应用最大截断模分析赤道波的基本形态,指出无论是正压模或斜压模Kelvin波、Rossby波及基本流所对应的

SHEAR INSTABILITY OF BASIC FLOW IN A TWO-LAYER EQUATORIAL OCEAN MODEL

A two-layer equatorial ocean model on the beta-plane is first derived,which consists of a mixed layer and a thermocline with different temperatures and densities,and then with the quasi-long-wave approximation,via low-order symmetrical truncation method,the basic mode of equatorial waves is studied.Research indicates that no matter for barotropic or baroclinic mode,the basic low-frequency waves in the tropics include Kelvin wave,Rossby wave,and topographic Rossby wave which depends on the basic flow;and under certain shear conditions there exists one kind of instability wave-coupled Kelvin-Rossby wave.With the approximation of the shallow mixed layer and the approximation of "fast wave",barotropic and baroclinic modes can be easily separated,and therefore their dispersion characteristics analyzed,respectively.Because of different values of characteristic parameter,the growth rates of the perturbations with the same wavelength(namely latitudinal scale of the perturbation) differ for barotropic and baroclinic modes,and under certain parameter value,the growth rate of perturbation for baroclinic mode is twice that for barotropic mode.Further research indicates that the growth of the flow field in the mixed layer is faster than that in the thermocline while the growth of temperature in the thermocline is more remarkable than that in the mixed layer,which provides theoretical basis for analyzing evolution of ENSO using subsurface temperature anomalies as done in recent years by many authors.