A NUMERICAL-ANALYSIS OF STRONGLY NONLINEAR BAROCLINIC INSTABILITY

To gain a better understanding of the general circulation in our atmos phere and of many other geophysical fluid dynamics phenomena, a stabil ity analysis of strongly nonlinear baroclinic flow in a rotating annul us has been performed. A dynamic model of baroclinic waves with single or wave-wave interactions is developed using an Eady-type basic state modified by two Ekman layers of different strengths. The mathematical model is developed in terms of the nondimensional stream function and is solved using a truncated spectral expansion. The expansion coeffic ients are computed from a set of evolution equations. The influences o f the imposed temperature contrast, the Ekman layer dissipation, and t he rotation rate on the main characteristics of the flow have been exp lored by solving the evolution equations for sequences of Ekman dissip ation rate, delta, and Stratification parameter, S. The current model not only produced the regimes observed in the annulus experiments: axi symmetric zonal flow, steady waves, and amplitude vacillation, but als o predicted the phenomena of wave number transition.