First phase of 2022 winteris least polluted in the last eight years. Smog-free phase; major cities record lower pollution levels
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New Delhi, December 12, 2022: 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 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.
“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 spikeslater 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 eventshave 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. 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).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.”
Key findings
Early phase of 2022 winter (October-November) was the least polluted in the last eight years in Delhi: Average PM2.5 levels across 37 functional CAAQMS stations of Delhi stood at 142 µg/m3 (microgramme per cubic metre) for the months of October and November. This is lowest level recorded since the city installed these stations in 2018. If data for the 10 oldest stations (working since 2014-15) is referred to, October-November of this year remains the least polluted in comparison. PM2.5 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 PM2.5 this year is 36 per cent lower than the same period in 2020. Similarly, 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. Nodia’s October-November average PM2.5 this year appears to be 40 per cent lower than the same period in 2020.However, it may be noted that one of Nodia’s CAAQM stations is reporting uncharacteristically low values this season. This needs to be examined.
Delhi was the most polluted major city in NCR with an October-November average of 142 µg/m3. Gurugram with 134 µg/m3 and Ghaziabad with 131 µg/m3 were the next most polluted cities in the NCR.
No severesmog episode (at least three consecutive days with air quality index at severe level) has been recordedso far during this season: There is usually one smog episode during October-November lasting six-10 days. This October-November, no episode was recorded in the city. This makes this October-November first in the last five years to be smog-free. During the previous winter of 2021, there were three smog episodes – two in November and one in December. November 2021 had recorded the longest smog episode of 10 continuous days (4-13 November, 2021). Such events have not occurred this winter.
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 (PM2.5 lesser than 30 µg/m3) -- this is the maximum number for winters in the last five years. Last year, there was one good air day while no good air days were recorded in the winters of 2018, 2019 and 2020. Only three days of severe or severe-plus days have been recorded so far, which is again the lowest in 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. These are respectively 37 per cent and 42 per cent lower than the figures for October-November of 2021. If the FRP (fire radiative power, which is the measure of intensity of fires) is taken into account in addition to the number of fires, it becomes clear that not only the fires were lesser in count but also lesser in intensity compared to the previous two years. The total FRP this October-November has been 363 kW and 187 kW according to VIIRS and MODIS, respectively. This is 45 per cent and 52 per cent lower than last year’s values recorded by the two satellites,respectively.
Fires have been lower this October-November both in count and intensity compared to previous two seasons, but are marginally higher compared to 2019 season.
Smoke intrusion from farm fires in Delhi lowest in last five years: Analysis of the SAFAR data shows that this year, smoke from the farm stubble fires contributed to PM2.5 levels in Delhi on 53 days, starting October 12 and ending on December 3. This is lesser than previous three years when smoke intrusion was reported on 56 days, but it is higher than 2018 figure of 48 days. Highest contribution this year was 34 per cent, reported on November 3. But given the overall low PM2.5 levels this year, 34 per cent contribution accounts for much less in terms of actual PM2.5 concentration in Delhi’s air. Therefore, it is critical to look also at the absolute mass of PM2.5 that got transported to the city from the fires.
The quantity of smoke from farm stubble fires that covers Delhi is dependent on two major factors: quantity and intensity of the fires, and meteorological conditions conducive for transportation of the smoke to Delhi. This October-November, not only the quantity and intensity of farm stubble fires have been comparatively lower but also the meteorological conditions have been less conducive for the transport of the smoke. As a result, total smoke that invaded Delhi has been considerably lesser. CSE has estimated that smoke has contributed about 4.1 tonne of PM2.5 during October-November in Delhi. This is 37 per cent lesser than the 6.4 tonne that came last year, and also almost half of the 2020 figure. The amount is significantly lower than the 2019 figure as well which is an indicator of meteorological help Delhi got as farm fires in 2019 were lesser.
High rainfall and local wind speed helped disperse local pollution: Delhi received 115 mm of rainfall this October-November, highest in the last five years. This helped cleanup the city air, especially in the month of October. Average wind speed for November stood at 12.4 km/hour which helped in dispersing local pollution. Average wind speed for 2021 November was 11 km/hour and for November 2020, 11.5 km/hour.
Hotspots continue to remain problematic: All hotspots have shown improvement compared to average pollution level recorded in 2018, 2019 and 2020. Mandir Marg has registered 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.
However, hotspots located in North and East Delhi were the most polluted in the city. Jahangirpuri was the most polluted neighborhood in October-November,with average PM2.5 level ranging at 186 µg/m3. Other most polluted hotspots were Bawana (172 µg/m3), Nerela (171 µg/m3), AnandVihar (166 µg/m3), Wazirpur (166 µg/m3), and Mundka (165 µg/m3). Mandir Marg with 103 µg/m3 and Bahadurgarh with 113 µg/m3 were the least polluted among the official hotspots.
Most polluted locations in NCR continue to be within Delhi’s city limits: Burari Crossing has been the most polluted location in NCR with an October-November average of 200 μg/m3. Jahangirpuri, Nehru Nagar, VivekVihar, Bawana, Narela, Alipur, Sonia Vihar, NSIT Dwarka, and AnandVihar round up the top 10 most polluted locations in NCR. All of them are located within the city limits of Delhi. Mandikhera and Palwal in south Haryana were the least polluted locations in NCR. Alwar in Rajasthan was the third least polluted location.
Least polluted Diwali in last six years: PM2.5 concentration on Diwali night (8pm to 8am) this year stood at 289 μg/m3, a good 61 per cent lower than last year’s Diwali night, when it was 747 μg/m3. Diwali night PM2.5 levels almost doubled the average night-time levels recorded in the week preceding Diwali. 2021 Diwali night levels were 4.5 times the average night-time levels recorded in the week preceding Diwali. This was a combined effect of Diwali happening much earlier in the season compared to previous years.
So what is the way ahead now?
Says Roychowdhury: “It remains to be seen how the rest of the winter will play out. But it is clear that to sustain this change and to improve further more deep rooted interventions are needed throughout the year. The region may have avoided the severe pollution levels. But poor and very poor levels as per the air quality index category are not acceptable from the public health standpoint. Milestones for action in each sector of pollution for the round the year action needs to be set and met urgently to have even cleaner winter next year.”
CSE says there is a need to acturgently in Delhi-NCR with the respect to the following:
For more information, please contact: Sukanya Nair, sukanya.nair@cseindia.org, 8816818864.
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