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Impact of La Nina on Indian Monsoon and Agriculture

Context

  • The Asia-Pacific Economic Cooperation (APEC) Climate Center, has forecast the return of the La Nina phenomenon in India.

Monsoon forecast for India

  • According to global weather agencies, India is likely to experience above-normal rains.
  • It is predicted for the region spanning eastern Africa to the Arabian Sea, India, the Bay of Bengal, and Indonesia, the Caribbean Sea, the tropical North Atlantic, southern Australia, and the southern South Pacific.

Ocean-Atmosphere system

  • Normal Conditions: During normal conditions in the Pacific Ocean, trade winds blow west along the equator, taking warm water from South America towards Asia.
  • To replace that warm water, cold water rises from the depths — a process called upwelling.
  • The warmer surface waters near Indonesia create a region of low-pressure area, causing the air to rise upwards. This also results in the formation of clouds and heavy rainfall.
  • The air flow also helps in building up the monsoon system which brings rainfall over India.
  • Abnormal Conditions: Both El Nino and La Nina usually begin to develop in the March to June season, reach their peak strength in the winter, and then begin to dissipate in the post-winter season.
  • Both these phases typically last for a year, though La Nina, on average, lasts longer than El Nino.
  • While these phases alternate over two to seven years, with the neutral phase thrown in between, two consecutive episodes of El Nino or La Nina can occur.

What is El Nino?

  • El Niño is the warming of seawater in the central-east Equatorial Pacific that occurs every few years.
  • During El Niño, surface temperatures in the equatorial Pacific rise, and trade winds — east-west winds that blow near the Equator — weaken.
  • Impact: El Niño causes dry, warm winters in the Northern U.S. and Canada and increases the risk of flooding in the U.S. Gulf Coast and southeastern U.S. It also brings drought to Indonesia and Australia.

What is La Nina?

  • La Niña is the opposite of El Niño. La Niña witnesses cooler than average sea surface temperature (SST) in the equatorial Pacific region.
  • Trade winds are stronger than usual, pushing warmer water towards Asia.
  • Impact: This leads to drier conditions in the Southern U.S. and heavy rainfall in Canada. It has also been associated with heavy floods in Australia.

How does it affect the Indian Monsoon?

  • In El Niño years, India faces warmer temperatures and less rainfall, causing droughts in some regions.
  • This affects agriculture, water resources, and ecosystems.
  • The El Nino phenomenon led to a 1.4% decrease in food grain production for the 2023-24 ( July-June) crop year.
  • La Niña brings cooler sea surface temperatures, leading to increased rainfall in certain parts of India.

How is La Nina beneficial for India?

  • Water resource management: Higher rainfall during La Niña events can improve water availability for irrigation.
  • Increased agricultural productivity: La Niña tends to bring above-average rainfall during the monsoon season, which is crucial for agriculture in India.
  • Lower food prices: Higher crop yields resulting from favorable weather conditions during La Niña events increase food supplies in the market.
  • Power generation: In India, hydropower contributes significantly to the energy mix. Increased rainfall during La Niña events boost water levels in reservoirs, improving hydropower generation capacity.