HOW DOES LA NINA AFFECT INDIA’S CLIMATE

La Niña

  • La Niña is a phase of the El Niño Southern Oscillation (ENSO).
  • It occurs when sea surface temperatures in the central and eastern Pacific Ocean (between Indonesia and South America) are cooler than usual.
  • Frequency:
    • La Niña events occur every 2-7 years but are less frequent than El Niño events.
    • Rarely, La Niña can persist for multiple consecutive years, known as a Triple Dip La Niña.
  • Duration:
    • A typical La Niña lasts 9-12 months but can sometimes persist longer.
  • Scientific Tracking:
    • La Niña is monitored based on oceanic and atmospheric indices, like:
      • Sea Surface Temperature Anomalies.
      • Oceanic Niño Index (ONI)

Impacts of La Niña on India

  • Monsoon Rainfall
    • La Niña years bring normal to above-normal rainfall during the monsoon season.
    • This helps improve agricultural output and water availability.
  • Temperature Patterns
    • La Niña causes colder-than-usual winters, particularly in northern India.
    • The cooler temperatures may lead to increased biomass burning, worsening air pollution.
  • Air Quality
    • During La Niña winters:
      • Lower Planetary Boundary Layer Height (PBLH) traps pollutants near the surface.
      • Combined with low wind speeds, pollutants are not dispersed, leading to poor air quality.
  • Wind Speed
    • Daytime wind speeds are reduced during La Niña compared to El Niño.
    • This slows the movement of pollutants, further impacting air quality.
  • Heat Waves and Summers
    • While El Niño summers are harsh with heat waves, La Niña that follows can bring relief in the subsequent summers.
  • Agriculture
    • Better monsoon rainfall during La Niña years supports crop yields and irrigation systems.
  • Droughts in Other Regions
    • While India receives above-average rainfall, droughts occur in Africa and hurricanes intensify over the Atlantic Ocean.
  • Rare Triple Dip Events
    • The recent Triple Dip La Niña (2020-2022) provided consistent rainfall but was unusual.
    • Such events can disrupt global climate patterns.

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