An equatorial pattern of enhanced and reduced convection and precipitation that travels eastwards across the tropical oceans. Particularly marked over the Indian and western Pacific Oceans, it becomes less distinct over the colder eastern Pacific, but strengthens again over the Atlantic. It moves at c.5 m/s over the eastern hemisphere and c.10 m/s over the western. Taken around the globe, there are typically one or two areas of enhanced convection and precipitation, and one or two regions where the effects are reduced. MJO activity is linked to the El Niño Southern Oscillation events, being typically strong about 6–12 months before the onset of an El Niño event, absent during an event, but becoming strongest during any La Niña phase.
Subjects: Meteorology and Climatology.