HOW THE MADDEN-JULIAN OSCILLATION HELPED TRIGGER THE EARLY ONSET OF THE MONSOON?

ORIGIN OF THE PHENOMENON

• What is MJO?
  The Madden-Julian Oscillation (MJO) is a system of winds, cloud, and pressure that moves eastward around the equator and influences rainfall patterns.
• Named After:
  Scientists Roland Madden and Paul Julian, who discovered it in 1971 while working at the National Centre for Atmospheric Research, Colorado.

HOW MJO WORKS

• Movement Speed:
  Travels at 4-8 metres per second, completing a global loop in 30–60 days (sometimes up to 90 days).
• Rainfall Phases:
  • Active Phase: Brings above-average rainfall.
  • Suppressed Phase: Results in less-than-average rainfall.
• Geographical Impact:
  Primarily affects tropical regions between 30° North and 30° South, which includes India.

INTERACTION WITH GLOBAL WEATHER SYSTEMS

• MJO & El Niño Correlation:
  • Some evidence suggests that strong MJO activity occurs during El Niño years.
  • However, not always directly correlated — El Niño often weakens the monsoon, even if MJO is strong.

 MJO’S ROLE IN EARLY MONSOON 2025

• Early Arrival Facts:
  • Kerala: Monsoon arrived on May 24, 8 days early.
  • Mumbai: Monsoon hit on May 26, the earliest on record.
• IMD’s Assessment:
  • Several atmospheric and oceanic factors contributed.
  • Key driver: The Madden-Julian Oscillation.
• Phase Details:
  • On May 22, the MJO entered Phase 4 in the Indian Ocean.
  • Its amplitude was greater than 1 — a sign of strong rainfall and storm activity.

 HISTORICAL PARALLEL: MJO IN 2015

• In June 2015, strong MJO activity led to 20 days of significant rainfall across most of India.
• Similar conditions in May 2025 likely initiated cyclonic activity that helped trigger an early monsoon onset.

SUMMARY

• The Madden-Julian Oscillation (MJO) played a crucial role in accelerating the southwest monsoon’s arrival in India.
• Its timely active phase over the Indian Ocean created favourable conditions for early and widespread rainfall.
• This emphasizes MJO’s growing relevance in monsoon prediction and climate modelling.