Dynamics of the tropical atmosphere and oceans This brief introduction to the climatology of the tropics identifies a number of phenomena that characterize the spatial and temporal variability of the tropical climate. Planetary scale circulations include Hadley like circulations the more zonal Walker systems westerly ducts tropical upper tropospheric troughs quasi biennial lower stratospheric oscillations and the monsoon systems. Each of these features is planetary in scale and oscillates on interannual time scales. Within these slowly varying features of the tropical atmosphere and ocean there is a myriad of circulation features with higher frequency variability. These include the Madden Julian Oscillation (MJO) quasi biweekly variability easterly waves tropical cyclones and depressions and a high amplitude diurnal cycle. These higher frequency scales of variability are not independent and are modulated by lower frequency events such as the MJO which in turn is modulated by the annual cycle and interannual variability. In subsequent chapters we will clarify the underlying mechanisms of these circulation features and their roles in weather and climate