The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.
Read more: About the MJO
The Maritime Continent is a term commonly used by meteorologists, climatologists, and oceanographers to describe the region between the Indian and Pacific Oceans including the archipelagos of Indonesia, Borneo, New Guinea, the Philippine Islands, the Malay Peninsula, and the surrounding seas. The region is made up of thousands of islands of various sizes, mountainous terrain, and many shallow seas. The terms maritime and continent are usually used to describe two opposite climate types. However together, they are used to describe the extensive interaction between ocean and land occurring across the Maritime Continent region.
The Maritime Continent is a significant feature in the Earth's climate system. As easterly trade winds along the equator blow along the ocean surface it creates a build-up of warm ocean waters in the western Pacific and among the shallow seas of the Maritime Continent. This region, known as the Indo-Pacific warm pool, persistently has sea surface temperatures (SSTs) higher than about 28°C and is often the warmest ocean region in the world.
Warm waters of the Maritime Continent add ample moisture and energy to the atmosphere creating an unstable environment where deep convective storms can develop at any time of the year. Large convective storms, which can be a daily occurrence on some islands, are triggered as the land surfaces heat or as the warm, moist air is forced upward by the terrain. This convective activity transfers large amounts of energy to the upper-atmosphere over the Maritime Continent and contributes to the east/west circulation in the tropical atmosphere, known as the Walker Circulation.
Variations in the east/west circulation (Walker circulation) have connections to other large-scale climate variations across the globe. The Maritime Continent region forms the western extent of SST anomalies associated with the El Niño-Southern Oscillation (ENSO) , and the eastern pole of SST anomalies associated with the Indian Ocean Dipole. As the SSTs across the Maritime Continent region change so too does the convection across the region. This creates shifts in the ascending region of the east/west global circulation and the associated global rainfall patterns.