Abstract: In this paper some basic properties of low frequency phenomena in the tropical atmosphere and coupled ocean-atmosphere system and attempts to seek a dynamical framework, in which the mechanisms leading to the 30-60 day oscillatoin and ENSO can be understood, are described, according to recent investegation in fo-reign literatures. Specific physical processes are identified and their roles in leading to the 30-60 day oscillation and ENSO are elucidated in a simple shallow-water system.A common thread linking the two phenomena is in the vital role played by moist processes in the atmosphere and how they can be affected by mean SST and interactive SST anomaly.