The Madden-Julian Oscillation (MJO) is a process that occurs several times each year from November-April in the atmosphere over the tropical Indian Ocean, the western tropical Pacific Ocean, and the surrounding land areas. MJO events alternate between periods of wetter-than-average and drier-than-average conditions, a cycle that lasts longer than typical weather systems do (1-2 weeks), but shorter than a season (90 days). The way that the MJO affects rainfall and drought patterns is important to the economies and livelihoods of the people that live in Southeast Asia, Indonesia, and Australia.
This animation shows the behavior of the MJO based on the average of many MJO events that occurred from 1979—2012. The MJO events were visible with polar-orbiting satellite sensors that measure cloudiness and rainfall using outgoing longwave radiation (OLR), which is closely related to convection and its associated rainfall. Therefore, green colors show regions of higher-than-average rainfall, while brown colors show regions of lower-than-average rainfall. The day counter shows the progression of consecutive days in the average 48-day cycle of the MJO, which since this dataset is an average over many years during winter, does not correspond to an exact date.