A new analysis by Delhi-based Centre for Science and Environment (CSE) has found that there are early signs of improvement in air quality in the first phase of this year’s winter in Delhi-NCR.

“So far, the average level of PM2.5 in this region has been the lowest in the last eight years. Also, the average level in the major cities, that are usually more polluted, has been cleaner in the last three years. The winter, so far, has not recorded any smog episode (when air quality index remains severe for at least three consecutive days or more) in contrast to prolonged episodes during the previous winter,” the analysis further found.

 “Diwali in a warmer October, lower incidents of crop fires that otherwise tip the local pollution over dangerous levels, pre-emptive action based on pollution forecasting, and favourable meteorological conditions including extended rainfall in October, have all contributed towards bending of the early winter pollution curve. But there may be more spikes later as has usually been observed in previous years. Stronger pre-emptive measures and deeper round the year action on local sources is needed to bring down the winter pollution to satisfactory levels,” says Anumita Roychowdhury, executive director, research and advocacy, CSE.

“This winter has started on a cleaner note with five ‘good’ AQI days in the first two weeks of October. Smog episode events have not been recorded so far. As per SAFAR estimates, smoke contribution from crop burning activities to Delhi’s PM2.5 level has gone down to zero as of November 4, 2022 and its overall contribution to Delhi’s PM2.5 concentration has been considerably lesser this time,” says Avikal Somvanshi, senior programme manager, Urban Lab, CSE.

 The objective behind the analysis has been to understand the changing patterns of winter pollution. This also helps locate the winter season within the longer term context of seasonal variations and annual trends in particulate pollution, says Somvanshi.

 Explaining the methodology and data sources behind the analysis, Somvanshi says: “This is an assessment of annual and seasonal trends in PM2.5 concentrations for the period October 1 to November 30 for 2018, 2019, 2020, 2021 and 2022. This analysis is based on real time data available from currently working air quality monitoring stations in Delhi-NCR.”

He said that a huge volume of data points have been cleaned and data gaps have been addressed based on the USEPA (United States Environmental Protection Agency) methodology for this analysis, which covers 81 continuous ambient air quality monitoring stations (CAAQMS) spread across Delhi-NCR.

“Meteorological data for the analysis is sourced from the Palam weather station of the India Meteorological Department (IMD). Fire count data is sourced from NASA’s Fire Information for Resource Management System, specifically Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS). Estimates of contribution of farm stubble fire smoke to Delhi’s air quality is sourced from the Ministry of Earth Science’s System of Air Quality and Weather Forecasting and Research (SAFAR),” he added.

“This is the first analysis of the third edition of Urban Lab’s Air Quality Tracker Initiative which was started in 2020-21 winter to study the impact of pandemic lockdowns on Delhi’s air quality,” Somvanshi said.