There are early signs of improvement in air quality in the first phase of this year’s winter in Delhi-NCR, says a new analysis by Centre for Science and Environment (CSE).
So far, the average level of Particulate Matter (PM) 2.5, 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 or AQI remains severe for at least three consecutive days or more) in contrast to prolonged episodes during the previous winter.
"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," says Anumita Roychowdhury, executive director, research and advocacy, CSE.
Roychowdhury also added, "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."
"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," says Avikal Somvanshi, senior programme manager, Urban Lab, CSE.
"As per System of Air Quality and Weather Forecasting And Research (SAFAR) estimates, smoke contribution from crop burning activities to Delhi’s PM 2.5 level has gone down to zero as of 4 November, 2022 and its overall contribution to Delhi’s PM 2.5 concentration has been considerably lesser this time," he added.
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 PM 2.5 concentrations for the period between 1 October and 30 November 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.
"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 Sciences' SAFAR.
"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.”
Early phase of 2022 winter (October-November) was the least polluted in the last eight years in Delhi. PM 2.5 level this October-November has been 15 per cent and 18 per cent lower compared to October-November of 2018 from a city-wide average of 37 stations and 10 oldest stations, respectively.
Levels have been 38 per cent lower compared to October-November of 2016 that was the worst autumn in the last eight years.
All major cities of Delhi-NCR that are more polluted than smaller towns, have recorded least levels in the last three years: Ghaziabad’s October-November average PM 2.5 this year is 36 per cent lower than the same period in 2020.
Greater Noida and Faridabad registered improvement of 28 per cent and 22 per cent respectively. This is higher than Delhi’s city-wide improvement of 19 per cent in the same time frame. Gurugram showed the least improvement with a mere 15 per cent change.
Noida’s October-November average PM 2.5 this year appears to be 40 per cent lower than the same period in 2020. However, it may be noted that one of Noida’s CAAQM stations is reporting uncharacteristically low values this season. This needs to be examined.
Five good air days recorded, highest in last five years: Heavy rainfall in October this year has resulted in five days of good air quality (PM 2.5 lesser than 30 µg/m3) — this is the maximum number for winters in the last five years.
Farm stubble fires this year are about half of the previous year: The total count of farm stubble fires reported this year from Punjab, Haryana and Delhi in months of October and November stood at 54,391, according to NASA’s VIIRS satellite and 11,824 according to NASA’s MODIS satellite.
Hotspots continue to remain problematic — But all hotspots have shown improvement compared to average pollution level recorded in 2018, 2019 and 2020.
Mandir Marg has registered the most improvement with its October-November levels this year being 36 per cent lower than average of 2018, 2019 and 2020.
Least improvement has been recorded in Mayapuri (6 per cent), Narela (7 per cent) and Ashok Vihar (8 per cent). Wazirpur, Faridabad and RK Puram registered an 11 per cent improvement, which is less than Delhi’s city-wide average of 16 per cent.
Arun Kumar Das is a senior journalist covering railways. He can be contacted at email@example.com.
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