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Using a 3-level model describing non-adiabatic finite amplitude ultra-long waves, the evolutionsof the wave amplitude and basic flow are obtained when the baroclinic zonal flow is slightly un-stable. It is shown that under circumstance of existing Newton heating, the rotating baroclinic at-mospheric system, which is heated by average axisymmetric heating and is weakly unstable, possessesdamping self-oscillation with characteristic periods from several weeks to several months. The effectof Newton heating may lead to a final equilibrium flow field, which is usually a high-index circu-lation and depends on the physical parameters of the atanosphere as well as the quantity of super-critical vertical shear of the basic flow. The precise natures of this evolutionary processes leading toequilibrium states depend on heating intensity (μ) and growing rate of the unstable baroclinic wave(kc_(oi)): in the case of general heating (i.e. μ<2~(1/2)kc_(oi)), the evolution of the ultra-long waveamplitude presents damping oscillation nature; while in the case of strong heating (μ≥2~(1/2) kc_(oi)),the whole evolutionary process appears in two stages, rapid and slow variakion stage. The aboveresults may be employed to explain theoretically some remarkable characteristics of the extended andlong-range variations of the general circulation of the atmosphere.
Using a 3-level model describing non-adiabatic finite amplitude ultra-long waves, the evolutions of the wave amplitude and basic flow are obtained when the baroclinic zonal flow is slightly un-stable. It is shown that under circumstance of existing Newton heating, the rotating baroclinic at-mospheric system, which is heated by the average axisymmetric heating and is weakly unstable, possessesdamping self-oscillation with specific periods from several weeks to several months. which effect is usually a high-index circu-lation and depends on the physical parameters of the atanosphere as well as the quantity of super-critical vertical shear of the basic flow. The precise natures of this evolutionary processes leading to unequilibrium states depend on heating intensity (μ) and growing rate of the unstable baroclinic wave (kc_ (oi)): in the case of general heating (ie μ <2 ~ (1/2) kc_ (oi)), the evolution of the ultra-long waveampli the whole evolutionary process appears in two stages, rapid and slow variable stage. The above results may be employed to (i) explain theoretically some remarkable characteristics of the extended and long-range variations of the general circulation of the atmosphere.