A DYNAMICAL ANALYSIS OF BASIC FACTORS OF LOW-FREQUENCY OSCILLATION IN THE TROPICAL ATMOSPHERE

Based on dynamical characteristics of the tropical atmosphere, a mathematical model of low-frequencyoscillation (LFO hereinafter) in low-latitudes has been developed. The analysis shows that the distributive fea-tures (shear of wind speed) of easterlies and westerlies in low-latitudes, the divergence and convergence ofmeridional and zonal flow, the vertical structure of diabatic heating and the Coriolis parameter f are thebasic factors resulting in the LFO, while quasi-periodical baroclinity development or index cycle of westerlywaves in middle-latitudes of the Southern Hemisphere is an external forcing to the LFO in the tropical atmos-phere. The resonance on adequate condition makes LFO suddenly enhanced.