On the Impact of La Nina on Air Quality in India

Source: This post on the Impact of La Nina on Air Quality in India has been created based on the article “La Nina impacted air quality in India: what a new study says” published in “Indian Express” on 20^th February 2024.

UPSC Syllabus Topic: GS Paper 1 Geography – Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.

News: The article discusses the impact of La Nina on Air Quality in India.

A detailed article on El Nino can be read here.

Read more about La Nina here.

Background:

Monsoon rainfall over India is known to be strongly influenced by El Nino and La Nina events (the alternating warming and cooling of the eastern Pacific Ocean that impacts weather across the world). A new study by Indian researchers has now suggested that even air quality could be influenced by the two weather events. Impact of La Nina on Air Quality in India

What does the study say?

It has argued that the unusual air quality in some Indian cities in the winter of 2022 could be attributed to the record-breaking spell of La Nina prevailing at that time.

This also links the air quality in Indian cities indirectly to climate change, which is making El Nino and La Nina more severe.

What are the reasons for bad air quality in Indian cities?

Various meteorological factors play a role in trapping pollutants in the lower atmosphere levels. These include:

1. Temperature.
2. Moisture.
3. Heaviness in air.
4. Wind speed and direction.

Situation in North Indian cities: During October to January, northern Indian cities, particularly Delhi, experience very high concentrations of PM2.5.

Situation in South Indian cities: The western and southern parts of the country usually have relatively lower levels of pollution, because of their proximity to oceans.

What was the change in the air pollution trend noticed in the winter of 2022?

Northern Indian cities, including Delhi, were cleaner than usual, while cities in the west and the south, like Mumbai, Bengaluru and Chennai, experienced worse-than-usual air quality. It was this unusual behavior that the researchers wanted to study.

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What is the explanation given for this?

1) Change in Wind Direction: During winter, wind usually blows in the northwesterly direction: for example, 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.

Source: Indian Express.

2) Changed Behavior of Local Circulation near Mumbai: The local circulation of wind currents near Mumbai alternate between blowing from the land to the sea every few days. In 2022, however, instead of changing direction every 4-5 days, the winds persisted in one direction for more than 7-10 days, leading to greater accumulation of pollutants in Mumbai.

The study says that the wind behavior in both cases was related to the extended La Nina which, by the winter of 2022, had been persisting for an unusually long 3 years.

Question for practice:

In what ways can La Nina effect Indian weather? Discuss in the context of changing wind patterns and air quality in India.