Role of Madden-Julian Oscillation (MJO) in Indian Monsoon

Role of Madden-Julian Oscillation (MJO) in Indian Monsoon
Posted on 18-08-2023

The Role of the Madden-Julian Oscillation (MJO)

The Madden-Julian Oscillation (MJO) is a significant oceanic-atmospheric phenomenon with far-reaching impacts on global weather patterns. Operating on weekly to monthly timescales, it introduces substantial variations in tropical weather.

Characterizing the MJO, it emerges as a disturbance encompassing clouds, wind, and pressure, advancing eastward at a velocity of 4-8 meters per second. Its journey spans an average of 30-60 days to complete a circumnavigation of the globe. At times, this voyage can extend to 90 days. This phenomenon traverses across regions, with its most pronounced effects felt over the Indian and Pacific Oceans.

The MJO's trajectory leads to a pivotal division of the planet into two distinct phases:

  1. Enhanced Rainfall (Convective) Phase: During this phase, surface winds converge, prompting vertical ascent throughout the atmosphere, and subsequently diverging at higher atmospheric levels. The upward motion of air in the atmosphere contributes to heightened condensation and, in turn, increased rainfall.

  2. Suppressed Rainfall Phase: Contrarily, the suppressed rainfall phase witnesses atmospheric winds converging at higher altitudes, instigating the descent of air that subsequently diverges at the surface. As the air descends from elevated altitudes, its temperature rises, accompanied by a reduction in humidity. This convergence of factors culminates in diminished rainfall.

The trajectory of the MJO is characterized by eight distinct phases. When positioned over the Indian Ocean during the Monsoon season, it translates into favorable conditions for substantial rainfall across the Indian subcontinent. However, when the MJO undergoes an elongated cycle and remains centered over the Pacific Ocean, it portends unfavorable implications for the Indian Monsoon.

In essence, the Madden-Julian Oscillation plays a pivotal role in shaping global weather patterns, with its dynamic phases influencing rainfall and convective activities across regions.

Relying on the Itinerant Madden-Julian Oscillation (MJO) for a Balanced Monsoon

The Arabian Sea segment of the south-west monsoon, according to the India Meteorological Department (IMD), is hinging on the migratory wave of the Madden-Julian Oscillation (MJO) to ensure a standard monsoon performance.

The MJO, a remarkable oceanic-atmospheric phenomenon, exercises a global impact on weather dynamics. Unveiling significant fluctuations in tropical weather over spans of weeks to months, the MJO manifests as an eastward-moving 'pulse' of clouds, precipitation, winds, and pressure near the equatorial region. This cyclical phenomenon recurs approximately every 30 to 60 days, undertaking a traversing trajectory that predominates over the Indian and Pacific Oceans.

The MJO's journey unfolds through distinct phases, with two cardinal parts:

  1. Enhanced Convective Phase: During this phase, surface winds converge, ushering upward motion throughout the atmosphere. The reversal of winds at higher atmospheric levels (divergence) promotes heightened condensation and amplified rainfall.

  2. Suppressed Convective Phase: Conversely, the suppressed convective phase witnesses atmospheric winds converging at elevated altitudes. This prompts the descent of air, inducing warming and reduced humidity. The subsequent divergence at the surface leads to diminished rainfall.

The complete dipole structure of the MJO, progressing from west to east across the Tropics, engenders varied weather patterns. This dynamic configuration results in enhanced cloudiness, rainfall, and even storms during the convective phase, while the suppressed phase is marked by sunshine and aridity.

The Impact of MJO on the Indian Monsoon:

In the realm of meteorological influences, the Indian Ocean Dipole (IOD), El Nino, and MJO each play a crucial role, but their scopes differ. The IOD pertains specifically to the Indian Ocean, while El Nino and MJO extend their effects globally to mid-latitudes. Notably, the MJO traverses across regions.

The progression of the MJO unfurls across eight distinct phases. When it intersects with the Indian Ocean during the Monsoon season, it augurs well for substantial rainfall across the Indian subcontinent. Conversely, when the MJO adopts an extended cycle, predominantly residing over the Pacific Ocean, it forecasts unfavorable implications for the Indian Monsoon.

The MJO's connection with heightened and suppressed rainfall activities in the tropics is of paramount significance for the Indian monsoonal rainfall. Its periodicity contributes to monsoon dynamics, whereby a cycle of nearly 30 days translates into fruitful Monsoon showers. Conversely, a cycle surpassing 40 days may lead to insufficient rainfall and even a parched Monsoon period. A shorter MJO cycle resonates with improved Indian Monsoon conditions, as it frequents the Indian Ocean more frequently during the four-month-long season.

The conjunction of an MJO presence over the Pacific Ocean and an El Nino scenario proves detrimental for Monsoon precipitation. Thus, the itinerant journey of the Madden-Julian Oscillation embodies a pivotal factor in shaping the Indian monsoonal outcomes.

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