What is the Madden-Julian Oscillation? | MJO Climate driver | Met Office | Learn About Weather

Summary

The Madden-Julian Oscillation (MJO) is a key atmospheric event influencing global weather patterns, primarily observed over the Indian and Pacific Oceans. Discovered in 1971, it features two regions of rainfall—one enhanced and one suppressed—that move eastward in a 30-60 day cycle. The MJO affects monsoons, tropical cyclones, and precipitation across various regions, including Africa, the Western USA, and Europe. It also contributes to El Niño development and influences mid-latitude weather systems, such as the North Atlantic Oscillation. The MJO’s impact on global weather makes it an essential driver of climate predictability.

Takeaways

• 😀 The Madden-Julian Oscillation (MJO) is an atmospheric phenomenon observed over the Indian and Pacific Oceans, discovered in 1971 by Roland Madden and Paul Julian.
• 😀 The MJO consists of two regions: one with enhanced rainfall and one with suppressed rainfall, which move eastward as the cycle unfolds.
• 😀 Each MJO cycle lasts 30-60 days and is divided into eight phases of equal length, each affecting different regions globally.
• 😀 The MJO typically begins over the Western Indian Ocean, moves through the tropical Pacific, and fades over the Eastern Pacific, with occasional re-emergence in the Tropical Atlantic.
• 😀 Satellites with infrared sensors can detect the MJO's enhanced or suppressed rainfall regions, as these are linked to convective clouds that emit little longwave radiation.
• 😀 The eight phases of the MJO correspond to different stages of enhanced rainfall that shift eastward across the globe, from the Western Indian Ocean to the Central Pacific.
• 😀 The MJO plays a significant role in the onset and breaks of summer monsoons, especially in India and Australia.
• 😀 The MJO's region of enhanced rainfall is conducive to tropical cyclone development, with its eastward movement shifting favorable conditions for cyclone generation.
• 😀 The MJO influences weather patterns in Africa, the Western U.S., and can affect the speed and intensity of El Niño and La Niña episodes.
• 😀 The MJO is linked to sudden stratospheric warming events, as evidenced by its role in the 2018 'Beast from the East' cold event in the UK.
• 😀 The MJO enhances predictability of mid-latitude weather systems, including the North Atlantic Oscillation, with specific MJO phases correlating to wetter or drier UK weather.

Q & A

What is the Madden-Julian Oscillation (MJO)?

The Madden-Julian Oscillation (MJO) is an atmospheric phenomenon characterized by two regions: one with suppressed rainfall and another with enhanced rainfall. It primarily occurs over the Indian and Pacific Oceans and moves eastward over a 30 to 60-day cycle.

Who discovered the MJO and when?

The MJO was discovered in 1971 by Roland Madden and Paul Julian, making it one of the more recently studied climate drivers.

How many phases does the MJO have, and how long does each phase last?

The MJO has eight phases, and each phase lasts for an equal length of time within the overall cycle, which lasts between 30 and 60 days.

Where does the MJO typically begin and how does it progress?

The MJO typically begins over the Western Indian Ocean and moves eastward across the tropical Pacific. As it moves over cooler ocean waters in the Eastern Pacific, its rainfall pattern becomes less distinct, except in warmer regions like the west coast of Central America.

What type of clouds are associated with the MJO, and why are they important for weather tracking?

The MJO is associated with convective clouds, which sit high in the atmosphere and emit little longwave radiation. These clouds are detectable by satellites with infrared sensors, which help track the regions of enhanced or suppressed rainfall.

What happens during Phase 1 of the MJO?

During Phase 1, enhanced rainfall develops over the Western Indian Ocean, marking the beginning of the oscillation cycle.

How does the MJO affect tropical cyclones?

The MJO influences the development of tropical cyclones by creating favorable conditions for their formation in the region of enhanced rainfall. As the rainfall area shifts eastward, it also shifts the region with favorable cyclone development conditions.

What is the relationship between the MJO and El Niño/La Niña events?

The MJO can contribute to the speed and intensity of El Niño and La Niña episodes. It also has a significant influence on their development and evolution, impacting global weather patterns.

What role does the MJO play in sudden stratospheric warming (SSW) events?

A strong MJO cycle can drive sudden stratospheric warming (SSW) events, which are linked to extreme weather, such as the 2018 'Beast from the East' event in the UK, causing freezing temperatures and heavy snowfall.

How does the MJO influence mid-latitude weather systems?

The MJO's teleconnections can enhance the predictability of mid-latitude weather systems, including weather patterns in Europe. The MJO affects the North Atlantic Oscillation, which influences the UK's weather, especially during phases 3 and 4 (milder, wetter) and phases 6 and 7 (colder, drier).