World Geography

Madden-Julian Oscillation (MJO) is an eastward moving pulse of cloud & rainfall in the tropics that recurs every 30 to 60 days. It is a traversing phenomenon and is most prominent over the Indian and Pacific Oceans.

MJO consists of two phases or parts as follows

• Enhanced rainfall or convective part: At this phase, winds at the surface coverage pushed up throughout the atmosphere.
  • After reaching the top of the atmosphere, the wind reverses.
  • Such rising air motion in the atmosphere tends to increase condensation and rainfall.
• Suppressed rainfall phase: Winds converge at the top of the atmosphere, forcing air to sink and, later, to diverge at the surface.
  • As air sinks from high altitudes, it warms and dries, which suppresses rainfall.
  • This phase brings more sunshine and dryness in the suppressed convective phase.

Difference between El-Nino and MJO

Although both El Nino and MJO are ocean-atmosphere interactions that occur in the equatorial region they differ on account of their

• Nature: While El Nino i.e. the unusual warming of sea-surface Pacific waters off the South American coast, is a stationary system, the MJO, on the other hand, is a moving system of wind, cloud and pressure that brings rain as it circles around the equator.
• Frequency: While El-Nino is associated with persistent features that last several seasons over the Pacific Ocean basin, MJO events occur within a season (i.e. weather varies on a week-to-week basis).
• Impact: Although the Indian Ocean Dipole (IOD), El-Nino and MJO are all oceanic and atmospheric phenomena, which affect weather on a large scale. IOD only pertains to the Indian Ocean, but the other two affect weather on a global scale-up to the mid-latitudes.

Impact of MJO on Indian Monsoon

As it moves, strong MJO activity often splits the planet into two zones: one in which the MJO is in active phase and brings rainfall, and the other in which it suppresses rainfall.

• When it is over the Indian Ocean during the Monsoon season, it brings good rainfall over the Indian subcontinent.
• On the other hand, when it witnesses a longer cycle and stays over the Pacific Ocean, MJO brings dry air and bad news for the Indian Monsoon.

MJO being a lesser-known phenomenon, it becomes important for the Indian Meteorological department to study more and to track it timely to predict its impact on Indian Monsoon.