Madden Julian Oscillation (MJO)

• Asymmetric ocean warming has driven contrasting changes in the regional propagation of the Madden–Julian Oscillation, with faster propagation over the Indian Ocean and Maritime Continent, but slower propagation over the Western Pacific.

About Madden-Julian Oscillation (MJO)

• The Madden–Julian Oscillation (MJO) is a major intraseasonal variability in the tropical atmosphere, characterised by an eastward-moving pulse of clouds, rainfall, winds, and pressure anomalies.
• Unlike long-term climate oscillations such as ENSO, the MJO operates on shorter time scales of 30–60 days, influencing weather and monsoon patterns worldwide.
• It was discovered in 1971 by Roland Madden and Paul Julian.

Phases of MJO

• Convective (Active) Phase: Rising moist air leads to cloud formation and heavy rainfall.
• Suppressed Phase: Sinking dry air reduces clouds and rainfall, leading to clearer skies.

Formation Mechanism

• Initiated by surface wind convergence in the tropics, causing upward motion and condensation.
• Supported by upper-level divergence, forming a dipole system that moves eastward between 30°N and 30°S.
• Regulates intra-seasonal rainfall variability and monsoon breaks, and can trigger early monsoon onset in India, as seen in 2024 and 2025.

Key Influencing Factors

• Sea surface temperature anomalies in the Indian and Pacific Oceans.
• Zonal wind changes and atmospheric moisture levels.
• Seasonal phenomena like El Niño can strengthen or weaken the MJO.

Influence of MJO

On Global Weather

• Tropical Cyclones: Alters frequency and intensity in Pacific, Indian Ocean, and Atlantic.
• ENSO Modulation: MJO pulses can trigger or suppress El Niño and La Niña events.
• Extreme Weather: Influences rainfall in Africa, droughts in Australia, hurricanes in America.
• Jet Streams & Mid-latitudes: MJO-driven wave trains affect weather in Europe and North America.

On the Indian Monsoon

• Onset of Monsoon: MJO pulses in the Indian Ocean enhance convection, aiding timely monsoon onset and promote cyclone formation.
• Breaks in Monsoon: Suppressed phases often correspond to breaks in rainfall over India.
• Intra-seasonal Variability: MJO explains fluctuations within a single monsoon season.
• Monsoon Extremes: Delayed pulses may cause drought-like conditions, while frequent active phases lead to excess rainfall.

MJO vs ENSO: A Comparison