Early Onset of Southwest Monsoon

Syllabus: GS1/Geography

Context

• Recently, the India Meteorological Department (IMD) announced that the Southwest Monsoon is expected to reach Kerala earlier than the normal onset date of June 1.

Monsoon in India

• The term ‘monsoon’ refers to the seasonal reversal of winds caused by differential heating and cooling of land and sea.
  • In India, monsoon rainfall is the backbone of the economy and climate system.
• India experiences two major monsoon systems:
  • Southwest Monsoon (June–September): Main rainy season contributing nearly 75% of annual rainfall.
  • Northeast Monsoon (October–December): Important mainly for Tamil Nadu and southeast India.
• The Southwest Monsoon is critical for agriculture, reservoirs, hydropower generation, and rural livelihoods.

Formation of the Southwest Monsoon

• Differential Heating: The Indian landmass heats faster than surrounding oceans, creating a low-pressure area over northwest India during summer.
• Shift of ITCZ: The Inter-Tropical Convergence Zone (ITCZ) shifts northward, attracting moisture-laden winds from the Indian Ocean.
• Cross-Equatorial Winds: Southeast trade winds cross the Equator and get deflected due to the Coriolis force, becoming southwesterly winds.
• Role of Jet Streams and Tibetan Plateau: The heating of the Tibetan Plateau and changes in subtropical jet streams strengthen monsoon circulation.

Branches of the Southwest Monsoon

• Arabian Sea Branch: It strikes the Western Ghats first, and causes heavy rainfall along the west coast. It advances towards central and northern India.
• Bay of Bengal Branch: It moves towards northeast India and the Indo-Gangetic plains. It is deflected by the Himalayas westward across northern India.

El Niño and Its Impact on Indian Monsoon

• El Niño refers to the abnormal warming of sea surface temperatures in the Equatorial Pacific Ocean.
  • It weakens monsoon circulation and often leads to below-normal rainfall in India.
• According to NOAA, 82% chance of El Niño developing during May–July.
  • IMD predicted seasonal rainfall at 92% of the Long Period Average (LPA), indicating below-normal rainfall.
• A strong or ‘super’ El Niño could reduce agricultural productivity, trigger drought-like conditions, affect groundwater and reservoirs, and increase food inflation and rural distress.
  • Regions like the Indo-Gangetic Plain are particularly vulnerable due to long-term drying trends.

Importance of the Indian Monsoon

• Agricultural Significance: Nearly 60% of Indian farmers depend on rainfall for sowing and irrigation.
• Economic Importance: Monsoon influences GDP growth, food production, rural demand, and inflation.
• Water Security: It replenishes rivers, groundwater, and reservoirs.
• Ecological Importance: Supports forests, biodiversity, and hydrological balance.

Source: DTE