India, Nov. 6 -- 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.

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 ...