Southwest Monsoon Ends with 12% Deficit

Syllabus: GS1/Climatology

Context

• As per the India Meteorological Department (IMD) India’s 2026 southwest monsoon ended with 759.4 mm of rain, 12.6% below the 868.6 mm normal.

About

• This is the lowest rainfall recorded during the monsoon season since 2015.
• The east and northeast region, which recorded 1,017.1 mm of rainfall, had its driest monsoon since 1901.

Monsoon

• The monsoon is a seasonal reversal of winds because of differential heating and the resulting pressure differences between land and sea.
• Onset and Retreat: The monsoon season in India generally starts in early June and lasts until September.
  • The onset of the monsoon is marked by the arrival of the southwest monsoon winds, which bring moisture-laden air from the Indian Ocean.
  • The withdrawal or retreat of the monsoon typically begins in October.
  • The northeast monsoon, occurring from October to December, brings rainfall to parts of southern India.
    • The northeast monsoon is key for Tamil Nadu, Kerala, Puducherry, Karaikal, coastal Andhra Pradesh, Rayalaseema, and Yanam in southern India.
    • The Northeast monsoon is also known as the winter monsoon, retreating monsoon, or reverse monsoon.

Factors Affecting Indian Monsoon

• El Niño: El Niño means “Little Boy” in Spanish. It is a climate phenomenon characterized by the periodic warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean.
  • During El Niño, trade winds weaken, and warm water is pushed back east, toward the west coast of the Americas, and as a result, cold water is pushed towards Asia.

• Impact of El Niño on weather patterns: It leads to a rise in global temperature, weakens the monsoon, increases the risk of wildfires, and triggers extreme weather events such as hurricanes and cyclones, particularly in the Pacific Ocean and Atlantic.
• Madden-Julian Oscillation (MJO): The MJO is a moving system of winds, clouds, and pressure that brings rain as it circles around the equator. It was discovered in 1971 by Roland Madden and Paul Julian.
  • The system travels eastward at 4–8 m/s and circles the globe typically every 30–60 days, though it can take up to 90 days.
  • As it moves, strong MJO activity often splits the planet into two parts — one in which the MJO is in active phase and brings rainfall, and the other in which it suppresses rainfall.
• During an active MJO phase, regions within its influence experience above-average rainfall, often due to increased cloud formation, convection, and cyclonic activity.

• Western Disturbance: A Western Disturbance (WD) is an extra-tropical weather system that originates outside India and moves from west to east, bringing rain, snowfall, and storms to northern parts of the Indian subcontinent.
  • Origin and Formation: Western disturbances originate over the Mediterranean region, Black Sea, or the Caspian Sea.
  • They form when cold polar air interacts with warmer, moist air, creating low-pressure systems.
  • These systems are carried eastward by westerly winds in the upper atmosphere, particularly the subtropical westerly jet stream.
• Indian Ocean Dipole: In 1999, N. H. Saji of Japan discovered an ENSO-like phenomenon in the Indian Ocean, which they named the Indian Ocean Dipole (IOD).
  • Like ENSO, IOD also has three phases—positive, negative, and neutral. During the positive phase of IOD, sea surface temperatures are warmer in the western Indian Ocean, which gives a boost to monsoon winds.
  • The reverse happens during IOD negative, and no gradient is observed during the IOD neutral period.
• Somali Jet: It is a fast-moving interhemispheric, cross-equatorial flow of air which originates near Mauritius and the northern part of Madagascar in the Southern Hemisphere. 
  • The winds cross the Equator and move along the eastern coast of Africa through Kenya, Ethiopia, and Somalia.
  • During May, the jet moves into the Arabian Sea, and by June it reaches the west coast of India.
  • As it travels, it carries a large amount of moisture (water vapour) from the ocean.
  • When the Somali Jet becomes stronger, it brings heavier and more reliable monsoon rainfall to Peninsular India.

Monsoons & the Economic Life in India

• Multiplier effect: Agricultural prosperity in India depends very much on timely and adequately distributed rainfall.
  • The success or failure of the monsoon directly shapes livelihoods at a national scale.

• Crop Diversity Advantage: Different rainfall zones allow India to cultivate a diversity of crops that few countries can match — a direct product of the monsoon’s geographic spread.
• Economic Growth :  

Conclusion

• The Indian monsoon isn’t just an important geographical phenomenon; it holds great economic value as well. 
  • About 64% of people in India depend on agriculture for their livelihoods, and agriculture itself is dependent on the southwest monsoon.
• A good monsoon raises agricultural production, aids GDP growth, and drives up rural earnings and consumption. Thus, it has been called the lifeline of the Indian economy.

Source: TH