What’s in Today’s Article?

• About La Nina (Meaning, Impact, Impact on India, etc.)
• Reasons for Delayed La Nina
• Conclusion

What is La Niña?

• La Niña is a phase of the El Niño-Southern Oscillation (ENSO) that occurs when sea surface temperatures in the eastern and central Pacific Ocean become cooler than usual.
• It is the opposite of El Niño, which brings warming in the same region. Both phases significantly influence global weather patterns.

How La Niña Affects Global Climate?

• India: Promotes normal to above-normal monsoon rainfall, leading to better agricultural yields.
• Africa: Causes drought-like conditions in certain regions.
• Atlantic Ocean: Intensifies hurricanes.
• United States: Southern states receive increased rainfall during La Niña.

La Niña and India’s Climate:

• Winter Effects:
  • Colder Winters: La Niña winters tend to bring colder nights in northern India but with slightly higher daytime temperatures.
  • Wind Speed and Pollution:
    • Higher Wind Speeds help disperse air pollution, improving air quality.
    • Lower Planetary Boundary Layer Height (PBLH) may trap pollutants closer to the ground, worsening pollution.
  • Current Scenario: In 2024, La Niña has not yet emerged as expected, with a 57% probability of it developing later in the year.
• Monsoons and Summers:
  • Enhanced Monsoons: La Niña years (like 2020-2022) have resulted in normal to above-normal rainfall.
  • Relief from Heat: La Niña reduces summer intensity, offering relief from heatwaves seen during El Niño years.
  • El Niño Impact: El Niño summers are hotter and often disrupt the monsoons, leading to droughts. For example, 2023, an El Niño year, saw below-normal rainfall.

Why Is La Niña Delayed in 2024?

• La Niña usually forms during the pre-monsoon or monsoon season.
• However, in 2024, it has been unusually delayed, with Oceanic Niño Index (ONI) hovering at -0.3°C (threshold for La Niña is -0.5°C or lower).
• If La Niña forms, it would bring the following:
  • Cooler winters in northern India.
  • Stronger monsoons in summer 2025.

Meteorological Indices to Identify La Niña:

• La Niña is declared based on specific indices such as:
  • Oceanic Niño Index (ONI): Measures average sea surface temperature anomalies
  • Persistence Rule: Values must consistently stay at or below the threshold (-0.5°C for La Niña) for five consecutive readings.

Climate Change and ENSO Events:

• Climate change is likely to increase the frequency and intensity of both La Niña and El Niño events due to rising ocean and atmospheric temperatures.
• Extreme La Niña events could amplify impacts like harsh winters and intense rainfall in India.

Significance of La Niña for India:

• Agriculture: Boosts crop production due to strong monsoons, aiding farmers.
• Water Resources: Improves reservoir levels, reducing water stress.
• Energy: More rainfall ensures better hydropower generation.
• Relief from Heat: Less severe heatwaves compared to El Niño years.

Conclusion:

• The delayed emergence of La Niña in 2024 has brought uncertainties regarding its impact on winter and monsoons.
• If La Niña sets in early 2025, it could ensure a strong monsoon season, crucial for India’s agriculture and water resources.
• Monitoring ENSO patterns is vital to understanding and preparing for its climatic effects.