This paper is an attempt to reveal the dynamic mechanism of low-frequency oscillation (LFO) in tropicalatmosphere. A two-level model on equatorial β-plane which includes the equation of water vapor evolution and theinteraction between condensational latent heating due to convection and large-scale dynamic processes is devel-oped. The difference in both heating capacity and moisture evaporation between underlying land and oceansurfaces is also taken into consideration. Firstly, the eigenmode in this model is analysed to reveal theeffect of convective heating on equatorial waves. It is found that with this heating, all the waves includingKelvin waves, Rossby waves, gravity waves and mixed Rossby-gravity waves, are slowed down, thus frequencydifferences between fast and slow waves are reduced. Therefore these waves are more likely to interact witheach other, causing the perturbations to propagate eastward very slowly and producing LFO. The comparisonbetween results of dry and moist model integration has confirmed the conclusion from dynamic analysis.
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