Context: The Madden‑Julian Oscillation (MJO) played a key role in triggering the early onset of the southwest monsoon in Kerala and Mumbai.
About the Madden‑Julian Oscillation (MJO)
What Is MJO?
- The MJO is an eastward‑moving tropical atmospheric disturbance involving clouds, rainfall, winds, and pressure patterns.
- Discovered in 1971 by Roland Madden and Paul Julian, it typically completes a global circuit every 30–60 days.
Phases of the MJO
- Enhanced Convective Phase: Increased rainfall and cloud formation due to rising air and moisture convergence.
- Suppressed Convective Phase: Reduced rainfall and clearer skies, as sinking dry air inhibits cloud development.
How Is the MJO Formed?
- Surface convergence of winds initiates rising air motion in the tropics.
- Condensation and cloud formation follow, supported by upper‑level divergence.
- The entire dipole system moves from west to east across the equator, especially between 30°N and 30°S latitude.
Factors Influencing the MJO
- Sea Surface Temperature (SST) anomalies in the Indian and Pacific Oceans.
- Atmospheric moisture content and zonal wind anomalies.
- Seasonal conditions like El Niño, which can amplify or suppress MJO activity.
Impacts of the MJO
On the Indian Monsoon
- An active MJO over the Indian Ocean can trigger early monsoon onset, as seen in 2024 and 2025.
- It boosts cyclogenesis and increases rainfall intensity during its passage.
- Improves intra‑seasonal rainfall variability and monsoon break patterns.
Global Influence
- Modulates cyclone frequency and strength across ocean basins.
- Alters jet streams, influencing weather extremes in the U.S., Europe, and Australia.
- Can cause cold surges, heatwaves, and floods in mid‑latitude regions.
- Acts as a short‑term climate modulator, unlike ENSO which has longer seasonal effects.
Conclusion
The Madden‑Julian Oscillation is a critical driver of tropical weather variability. Its enhanced convective phase spurred the early southwest monsoon in Kerala and Mumbai, while its global impacts extend from cyclones to mid‑latitude extremes. Monitoring the MJO remains essential for accurate seasonal forecasts and climate preparedness.
