Still night, winds from farm-fire belt push Delhi's AQI to 389 | Latest News Delhi

Delhi's air got worse through Thursday night. By 7am on Friday, the Central Pollution Control Board's (CPCB) hourly AQI had climbed to 389, 20 points above the 369 in Thursday's 4pm bulletin. The wind near the ground fell almost still, and a layer of warm air held the night's pollution close to the city.

At 7am, 28 of Delhi's 59 reporting stations were in the "severe" category, which means above 400 on CPCB's 500-point scale. (ANI)Higher up, the wind blew in from the north-west, from Punjab and Haryana, where Nasa's satellite counted 226 farm fires on Thursday. The India Meteorological Department (IMD) sent up a weather balloon from Safdarjung at 4.30am, and it measured winds of 23 km/h between 500 and 1,500 metres above the ground. Winds at that height are known as transport-level winds, and they carry smoke over long distances.

The satellite's daily count of fires in the two states has nearly doubled in a week, from 120 on October 30 to 246 on both November 3 and 4, according to the HT Pollution Dashboard's tally of Nasa data. Since October 1, it has detected 2,477 fires, 2,232 of them in Punjab.

Those numbers understate the burning. Nasa's satellite passes over in the early afternoon, and farmers have been burning later in the day each year, after it has gone.

At 7am, 28 of Delhi's 59 reporting stations were in the "severe" category, which means above 400 on CPCB's 500-point scale. IIT Delhi and Rohini were the worst, at 474 each, followed by Punjabi Bagh (465) and Jahangirpuri (460), and every station in the city was "very poor" or worse.

CPCB's hourly figure for each station is a running average of the past 24 hours, updated every hour. An HT Pollution Dashboard analysis of those readings shows 18 severe stations at 4pm on Thursday, rising to 28 by 5am, the most at any hour in the past week. ITO, Mandir Marg, JNU and Okhla Phase-2 were among the 10 that crossed 400 overnight.

Near the ground, the air barely moved. Safdarjung airfield logged calm air in seven of its 10 weather reports between 8pm and 6.30am, and the wind averaged 1 km/h, well short of the 15 km/h or more that helps clear Delhi's air. By 7.30am, it had picked up only to 4 km/h.

The 4.30am balloon also found a layer of air about 250 metres above the ground that was 6°C warmer than the surface, slightly warmer than on Thursday morning. Air usually cools with height, which lets pollution rise and spread out. A warm layer above cooler air, called a temperature inversion, works like a lid and holds pollution near the ground.

PM2.5, or fine particles, was the main pollutant at 53 of the 59 stations.

Thursday's bulletin averages readings over the 24 hours to 4pm. It put Delhi's AQI at 369, the fourth worst among the 283 cities CPCB reported.

Afternoon sunshine usually helps clear the air. It heats the ground, and the rising warm air carries pollution into a deeper layer, where it thins out. On Thursday afternoon that layer reached only about 850 metres, against about 1,300 metres usual for early November, though the wind through it was close to normal.

Friday's 4pm bulletin will average the 24 hours from Thursday afternoon, including the still night.

Check the air at your nearest station, hour by hour, on the HT Pollution Dashboard at hindustantimes.com/breath

Binayak Dasgupta is a senior editor at Hindustan Times, New Delhi, where he has worked since 2013. He heads the paper's Page 1 team and is part of the editorial leadership overseeing daily news operations. He has previously led the national news desk. His work sits at the intersection of specialist depth and emerging public consequence — stories where complexity and nuance are in themselves the journalistic challenge. He shapes Hindustan Times's coverage and editorial positions on technology and artificial intelligence, information security, environment, health and science — steering these subjects from the commissioning of reporting to editing and the framing of the paper’s institutional view. His work spans analysis, commentary and reportage and in the past has led the paper's coverage of Covid-19 pandemic science. His interviews and hosted sessions include Nobel laureates, technology leaders, economists and climate justice scholars. In recent months, Binayak has overseen the coverage of the Air India Flight 171 crash and its investigation, India's energy exposure during the West Asia conflict, the trade dispute with the US, Delhi's air quality emergency and the evolving conversations around AI, including the IndiaAI Summit.Read More

Saloni Bhatia is a journalist with over 15 years of experience in reporting and storytelling, with a strong focus on the Delhi government and political developments in the Capital. Over the years, she has closely tracked policy decisions, governance issues, and political shifts. She started off as an entertainment journalist but then moved to covering beats like crime and education. Her experience on the crime beat helped her develop an eye for detail and accuracy, while education reporting allowed her to explore policy impact on students, teachers and institutions. Outside the newsroom, she enjoys reading both fiction and non-fiction. She also has a keen interest in watching Bollywood films.Read More