Question – What is the Madden Julian Oscillation? How does it affect rainfall? – 25 March 2022
Answer – The Madden Julian Oscillation (MJO) is one of the most important atmosphere-ocean linked events in the tropics, which has a profound effect on the Indian summer monsoon. The MJO is a mode of climate change associated with tropical weather, typically lasting 30 to 60 days, which was discovered by Madden and Julian in 1971 and published a paper on it.
The Madden Julian Oscillation has the following characteristics:
- The MJO is a large-scale weather event, consisting of intense convection with atmospheric circulation, which gradually moves eastwards over the Indian and Pacific Oceans.
- The MJO is an equatorial pattern of irregular rainfall, which is a continuous-flowing phenomenon, and is most dominant in the Indian and Pacific Oceans. Therefore the MJO is a moving system of wind, clouds and pressure. As it moves around the equator, it starts raining.
- Each cycle lasts about 30 to 60 days. It is also known as 30-60 day oscillation, 30-60 day wave or inter-seasonal oscillation (ISO).
Phases of Madden-Julian Oscillation (MJO)
- There are mainly two phases or phases of the MJO: one is the phase of convection or enhanced rainfall, and the other is the phase of suppressed rainfall.
- Strong MJO activity often disintegrates the planet in half: one half the increased convective phase and the other half the suppressed convective phase. These two phases produce opposite changes in clouds and precipitation, and this entire dipole extends eastwards.
- In Phase 1 an area of precipitation developed due to convection over the western Indian Ocean of the MJO.
- In Phases 2 and 3, the area of rainfall gradually increases to the east and over parts of Africa, the Indian Ocean and the Indian subcontinent.
- In Phases 4 and 5, the area of rainfall reaches Indonesia and the West Pacific Ocean.
- In Phases 6, 7 and 8, precipitation advances east over the West Pacific Ocean and then finally dissipates in the Central Pacific.
Effect of Madden-Julian Oscillation on Indian Monsoon:
- The Indian Ocean Dipole (IOD), El-Nino and Madden-Julian Oscillation (MJO) are all oceanic and atmospheric phenomena that largely affect the weather.
- The IOD and El Nino remain in their former positions, while the MJO is a continuous physical phenomenon.
- When it occurs over the Indo-Ocean during the monsoon, the entire Indian subcontinent receives good rainfall. On the other hand, when it occurs as a long cycle time period, and stays over the Pacific Ocean, the rainfall loss in the Indian monsoon season is less. It performs rainfall activities in the tropics with a high but repressed nature, which is very important for the Indian monsoon rainfall.
Effect of MJO on World Weather:
- There are many ways MJOs affect the weather around the world. For example, the MJO creates favorable conditions for a tropical cyclone.
- The arrival of monsoon is controlled by the MJO. It also affects the El Nino Southern Oscillation (ENSO).
- The MJO helps to generate and intensify El Nino and La Nina.
