News: The southwest monsoon arrived early, reaching Kerala on May 24 and Mumbai by May 26 — the earliest ever. The IMD says this was mainly due to favourable weather patterns, especially the Madden–Julian Oscillation.
About Madden-Julian Oscillation (MJO)
- It is a tropical atmospheric phenomenon characterized by a moving system of winds, clouds, and pressure that brings rainfall as it moves eastward along the equator.
- It was discovered in 1971 by scientists Roland Madden and Paul Julian at the National Centre for Atmospheric Research in Boulder, Colorado.
- The MJO typically completes one global cycle in 30 to 60 days, although it can sometimes take up to 90 days.
- As it moves, the MJO creates two distinct zones — one where rainfall activity is enhanced (active phase) and another where rainfall is suppressed (suppressed phase).
- The MJO travels eastward at a speed of about 4 to 8 metres per second and primarily influences weather patterns in the tropical belt between 30°N and 30°S latitude, which includes India.
- The MJO has a significant impact on tropical weather systems, including monsoons, cyclones, and periods of heavy rainfall or dryness.
Phases and Impact of MJO
- During its active phase, the MJO leads to increased cloud formation, strong convection, and higher-than-average rainfall in the affected region.
- In its suppressed phase, the MJO inhibits convection and results in lower-than-average rainfall or dry conditions.
- These alternating phases occur periodically and can influence multiple weather events within a single season.
