The Tropics are characterized by some of the most intriguing atmospheric phenomena of our planet. Among them the Asian monsoons and the El Niño/Southern Oscillation (ENSO) are certainly the most important, since food production and water resources in most of the tropical and subtropical countries depend fundamentally on their occurrence and strength. Nevertheless, as many recent studies have pointed out, they are only the most spectacular components of a more general multi-scale system, where phenomena of different spatial and temporal scales interact and appear to be inter-dependent. The quasi-periodic phenomena in the atmosphere have always been particularly interesting to the meteorological community; specifically, the atmospheric oscillations with time scales ranging from one week...