Triple-dip La Nina led to better winter air in 2023: Elsevier Journal study

A team of scientists led by Gufran Beig, chair professor of the National Institute of Advanced Studies, worked on the project

The air quality in the National Capital Region (NCR) improved significantly last winter due to a rare weather phenomenon, known as a “triple-dip” La Nina, that reduced pollution levels in north India, but propelled them up in the peninsular parts of the country, said a study released on Sunday.

Lodhi Garden prominently visible on a clear day in the Capital in February last year. (Sanchit Khanna/HT Photo)

The triple-dip, or three consecutive years of La Nina, deeply impacted oceans and the climate across the globe, said the study titled “Triple dip La-Nina, unorthodox circulation and unusual spin in air quality of India”, published in the Elsevier Journal.

A team of scientists led by Gufran Beig, chair professor of the National Institute of Advanced Studies, worked on the project.

“The winter of 2022-23 coincided with the last phase of an unusual triple-dip La Nina event, the first in the 21st century. This phenomenon, influenced by climate change, impacted the large-scale wind pattern, playing a decisive role in preventing stagnation conditions in north Indian cities, thus improving air quality,” said RH Kripalani, a climate scientist at the Indian Institute of Tropical Meteorology and co-author of the report.

“The dominance of higher northerly winds at the transport level forced an influx, along with relatively slower winds near the surface, trapping pollutants in peninsular India and increasing PM2.5 concentration. Conversely, feeble western disturbances, unique wind patterns, and the absence of rain, clouds, and faster ventilation led to a significant improvement in air quality in the north,” Kripalani said.

Among the north Indian cities, Ghaziabad’s air improved most significantly, with PM2.5 (an ultrafine pollutant) levels dipping 33%, followed by Rohtak (30%) and Noida (28%). Delhi’s air improved by around 10%.

On the contrary, Mumbai recorded the worst deterioration with a 30% jump in PM2.5 levels, followed by other peninsular Indian cities like Coimbatore (28%), Bengaluru (20%) and Chennai (12%), among others.

The scientists used the newly developed advanced NIAS-Safar air quality forecasting model, which combines a chemical-transport model with an indigenously developed modern artificial intelligence algorithm.

“Our findings are vindicated as the air quality in the winter of 2023-24, when La Nina ended, returned to normal levels,” Beig said.

“The findings of the current paper suggest that we need to wake up to the fact that extreme and unusual occurrences in air pollution phenomena are directly or indirectly manifestations of climate change,” he said.

“Such revelations, in all probability, are set to increase by leaps and bounds unless we focus on a long-term strategy to reduce the menace of anthropogenic emissions directly at the source. That would be a win-win situation for both air quality and climate change,” he said.