Air Pollution

La Nina impacted Air Quality in India: Study


From UPSC perspective, the following things are important :

Prelims level: El Nino and La Nina

Mains level: Link Between ENSO and local Air Pollution

la nina


  • El Nino and La Nina events have long influenced India’s monsoon patterns, but a recent study suggests a novel connection between these weather phenomena and air quality, particularly during the winter months of 2022.

Understanding El Nino and La Nina

  • El Nino and La Nina are two opposite phases of the El Nino-Southern Oscillation (ENSO) cycle.
  • ENSO is a naturally occurring phenomenon that involves the interaction between the ocean and atmosphere in the equatorial Pacific.

Here is a detailed comparison of El Nino and La Nina

El Nino La Nina
Definition Warmer-than-normal sea surface temperatures Cooler-than-normal sea surface temperatures
Frequency Every two to seven years Every two to seven years
Duration Several months to a year or more Several months to a year or more
Impact on winds Weakens trade winds, leading to changes in patterns Strengthens trade winds, leading to changes in patterns
Impact on rains Reduces rainfall and can cause droughts Increases rainfall and can cause flooding
Impact on temp. Warmer-than-average temperatures Colder-than-average temperatures
Global effects Droughts in Asia and Africa, floods in Americas Floods in Asia and Africa, droughts in South America

Impact on India

El Nino La Nina
Associated with weak monsoons and drought-like conditions in India Associated with above-normal rainfall and floods in India
Sea surface temperature in the equatorial Pacific Ocean rises above normal levels Sea surface temperature in the equatorial Pacific Ocean drops below normal levels
Changes in the atmospheric circulation patterns Changes in the atmospheric circulation patterns
Shift in the location of the jet stream, affecting the strength and direction of the monsoon winds Increase in the strength of the monsoon winds, bringing more moisture and rainfall to India
Results in reduced rainfall, dry spells, and heatwaves, leading to crop failures and water scarcity Excessive rainfall can also lead to floods and landslides, causing damage to crops and infrastructure

El Nino and Indian Monsoon

  • El Nino and its impact on Indian monsoon: El Nino refers to abnormal warming of surface waters in the equatorial Pacific Ocean, which tends to suppress monsoon rainfall in India.
  • Phases of El Nino Southern Oscillation (ENSO): ENSO consists of three phases in the Pacific Ocean: El Nino, La Nina (abnormal cooling), and a neutral phase with sea surface temperatures close to long-term averages.
  • Ocean and atmospheric conditions: ENSO involves not only temperature abnormalities of sea surface waters but also atmospheric conditions, including differences in sea-level air pressure and wind strength and direction.
  • Southern oscillation and the role of winds: Southern Oscillation Index measures the difference in sea-level air pressure over the western and eastern sides of the Pacific Ocean, while wind patterns play a crucial role in ENSO.

How La Nina impacted air quality?

  • Wind Direction Shift: The study identified a significant alteration in wind circulation patterns during the winter of 2022, with winds typically blowing from the northwest direction diverted towards the south due to the prolonged La Nina effect.
  • Anomalous Behavior: This deviation led to a bypass of pollutant-laden winds from Punjab and Haryana away from Delhi towards southern regions, impacting cities like Mumbai, Bengaluru, and Chennai.
  • Extended La Nina Effect: The persistence of La Nina conditions over three years intensified the impact on wind patterns, culminating in noticeable changes in air quality distribution across India.
  • Uncertainties and Further Exploration: While the study highlights the role of La Nina in altering wind circulation and subsequent air quality, uncertainties remain regarding the potential impact of El Nino events on air quality dynamics.


  • The study underscores the need for continued exploration into the interplay between global weather phenomena like La Nina, local meteorological conditions, and air quality dynamics in India.
  • Understanding these complex relationships can inform policy measures aimed at mitigating air pollution and enhancing environmental resilience in the face of climate change challenges.

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