STUDY OF CHARACTERISTIC MODES IN SIMPLE TROPICAL COUPLED AIR-SEA MODEL

The propagation features, stabilities and dynamical characteristic structures of coupled Kelvin inner modes and second order Rossby inner modes are studied using a simple tropical coupled air-sea model in this paper. It is shown that there is mechanism of selecting scale and frequency in the tropical air-sea system. The effects of air-sea coupling are mainly on the large-scale modes and nonuniform. These effects make the frequency of Kelvin modes decrease and even excite the eastward propagating Rossby inner modes. These effects make the unstable development of Kelvin modes and result in the decay of Rossby modes. The effects of atmospheric damp are opposite to those of air-sea coupling. The oceanic damp only make the wave amplitudes decay. Simutaneously, this paper shows the dynamical characteristic structures of air-sea coupled system and the phase relations between the atmospheric and the oceanic wave component.