CSE releases latest analysis of air quality data for Delhi-NCR, as winter sets in

CSE says 2021 winter season starting with much cleaner threshold compared to the previous three years

By DTE Staff
Published: Friday 22 October 2021
Photo: istock__

Delhi-based non-profit Centre for Science and Environment (CSE) released the latest analysis of air quality data for the National Capital Region October 22, 2021 with the onset of winter.

The analysis is an assessment of annual and seasonal trends in Particulate Matter (PM) 2.5 concentration for the period January 1, 2018 to October 15, 2021, according to a statement by CSE. PM2.5 refers to atmospheric PM that have a diameter of less than 2.5 micrometers

It captures three successive winter seasons, pre-winter trends and pre and pandemic era including stages of lockdown in Delhi and NCR. The analysis is based on the real time data available from the current working air quality monitoring stations in Delhi-NCR and the larger Indo Gangetic Plain.

The analysis covers 156 continuous ambient air quality monitoring stations spread across 67 cities in Punjab, Chandigarh, Haryana, Delhi, Rajasthan, Uttar Pradesh, Bihar and West Bengal.

Seasonal PM2.5 averages of cities in the Indo-Gangetic Plain


Anumita Roychowdhury, executive director, research and advocacy, CSE, said: “The objective has been to understand the starting line of the onset of the winter pollution season or pre-winter levels in this region, and also to understand the longer term trends in seasonal variations.”

She added that the 2021 winter was starting with a cleaner threshold compared to the previous years, largely due to the intense and prolonged effect of the monsoons.

Roychowdhury noted:

While winter pollution cannot be predicted at this moment, the evidence of rising summer pollution in 2021 despite the lockdown and the evidence of a synchronised effect of winter pollution across the Indo-Gangetic Plain add to our concern. How soon and intensely the winter pollution will hit us will depend on the scale and speed of action across the region and leveraging it for more sustained air quality gains.

In the analysis, the winter season is considered from October 15 to February 15, based on dates referred in Delhi’s Graded Response Action Plan. Summer season is considered from February 16 to June 30. The monsoon period and the phase of extended rains cover the period from July 1 to October 15.

Meteorological data for the analysis has been sourced from the Palam weather station of the India Meteorological Department. Fire count data has been sourced from the National Aeronautics and Space Administration’s Fire Information for Resource Management System. Specifically, Visible Infrared Imaging Radiometer Suite (VIIRS) has been used.

The estimate of contribution of farm stubble fire smoke to Delhi’s air quality is sourced from the Union Ministry of Earth Science’s System of Air Quality and Weather Forecasting and Research.

Avikal Somvanshi, programme manager at the Urban Data Analytic Lab at CSE, said:

This winter we may get a much severe peak in smog, as farm stubble fire counts may get more concentrated due to the delayed effect of the rains — to counter this, action must be scaled up right away.

Roychowdhury added that Delhi and the larger region would require urgent action to prevent severe smog episodes as well as speed up deeper reforms to sustain the gains.

“Reduce traffic volume, eliminate waste burning, eliminate dirty industrial fuels and implement stringent dust control measures — especially in the construction sector. Act now, and act decisively,” she said.

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