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La Nina impacted air quality in India |

La Nina impacted air quality in India

Context

  • An unprecedented triple-dip La-Nina event, extended by climate change, has impacted the air quality in India.

  • Link between pollution and winter months in India
  • During October to January, northern Indian cities experience very high concentrations of PM2.5. A variety of meteorological factors — temperature, moisture, heaviness in air, wind speed and direction — play a role in trapping pollutants in the lower levels of the atmosphere. These factors are also responsible for transporting pollutants from other regions, particularly those generated by agriculture waste burning in Punjab and Haryana, to Delhi and adjoining areas.On the other hand Western and Southern parts of the country have always had relatively lower levels of pollution, because of their proximity to oceans.

  • Rare ‘triple dip’ La Niña 
  • The winter of 2022-23 coincided with the last phase of an unusual triple-dip La Niña event, the first in the 21st century.The air quality worsened in peninsular Indian cities in the 2022-23 winter season but improved in the northern part of India.This phenomenon, influenced by climate change, impacted the large-scale wind pattern, playing a decisive role in preventing stagnation conditions in north Indian cities and thus improving air quality.

    El Niño, La Niña & ENSOEl Niño– 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. – 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.– In India, it causes weak rainfall and more heat.La Niña– 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.– 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. – In India, La Niña intensifies rainfall particularly in its northwest.El Niño Southern Oscillation (ENSO)– The combination of El Niño, La Niña, and the neutral state between the two opposite effects is called ENSO. – Southern oscillations are large-scale changes in sea level pressure in the tropical Pacific region.La Nina impacted air quality in India |

  • Wind direction
  • A change in the normal wind direction led to the anomaly of winter 2022.During this time, wind usually blows in the northwesterly direction, from Punjab towards Delhi and further into the Gangetic plains. In the winter of 2022, however, the wind circulation was in the north-south direction. The pollutants being carried from Punjab and Haryana bypassed Delhi and surrounding areas and flew over Rajasthan and Gujarat to southern regions.In the case of Mumbai, usually wind currents alternate between blowing from the land to the sea every few days. When blowing from the land towards the sea, the winds carry pollutants out of the city. In 2022, however, instead of changing direction every four to five days, the winds persisted in one direction for more than a week or 10 days, leading to greater accumulation of pollutants in Mumbai.

  • La Nina impacted air quality in India |

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