Why in news?
The Madden-Julian Oscillation (MJO) significantly contributed to the early arrival of the southwest monsoon in Kerala and Mumbai, accelerating rainfall and weather patterns over these regions.

About Madden-Julian Oscillation (MJO):

• What is MJO?
  The Madden-Julian Oscillation is an eastward-moving tropical atmospheric disturbance. It involves patterns of clouds, rainfall, winds, and pressure that travel around the globe.
• Discovery:
  Identified in 1971 by meteorologists Roland Madden and Paul Julian.
• Cycle Duration:
  The MJO completes one full cycle around the Earth every 30 to 60 days.
• Phases:
  
  1. Enhanced Convective Phase: Increased rainfall and cloud formation occur due to rising moist air.
  2. Suppressed Convective Phase: Rainfall decreases and skies clear as dry air sinks, reducing cloud formation.

How is the Madden-Julian Oscillation (MJO) Formed?

• Surface winds converge in the tropics, causing air to rise.
• Rising air cools and condenses, forming clouds and rainfall.
• Upper-level divergence (air spreading out at high altitudes) supports this upward motion.
• This system of enhanced and suppressed convection moves eastward across the equator, mainly between 30° North and 30° South latitudes.

Factors Influencing the Madden-Julian Oscillation (MJO):

• Sea Surface Temperature (SST) anomalies, especially in the Indian and Pacific Oceans, affect the strength and movement of the MJO.
• Atmospheric moisture levels and zonal wind anomalies play a crucial role in modulating convective activity.
• Seasonal phenomena such as El Niño can either amplify or suppress the MJO’s intensity and behaviour.

Impacts of Madden-Julian Oscillation (MJO):

On Indian Monsoon:

• The MJO’s active phase over the Indian Ocean can trigger an early monsoon onset, as witnessed in 2024 and 2025.
• It enhances cyclogenesis, leading to stronger and more frequent cyclones and increased rainfall intensity.
• It improves intra-seasonal rainfall variability, causing fluctuations like monsoon breaks and bursts.

Global Influence:

• MJO modulates cyclone frequency and strength across various ocean basins worldwide.
• It alters jet streams, affecting weather extremes in regions such as the U.S., Europe, and Australia.
• It can trigger cold surges, heatwaves, and floods in mid-latitude areas.
• Unlike ENSO, which influences seasonal climate, the MJO acts as a short-term climate modulator with impacts lasting weeks.