New Delhi: The share of stubble burning in Delhi's pollution rose to 40 per cent on Sunday, the maximum so far this season, according to a central government air quality monitoring agency.

The Ministry of Earth Sciences' air quality monitor, SAFAR, said 3,216 farm fires were spotted over Punjab, Haryana, Uttar Pradesh and Uttarakhand on Saturday.

The share of stubble burning in Delhi's PM2.5 pollution was 40 per cent on Sunday, the maximum so far this season. It was 32 per cent on Saturday, 19 per cent on Friday and 36 per cent on Thursday, the second highest this season so far.

Last year, the stubble contribution to Delhi's pollution had peaked to 44 per cent on November 1, according to SAFAR data.

NASA's satellite imagery showed a large, dense cluster of fire dots covering Punjab and parts of Haryana and Uttar Pradesh. 

SAFAR said air quality has not improved much despite improved ventilation due to high stubble-related intrusion and trapping of pollutants during night time due to low wintertime boundary layer height.

"However, it has not deteriorated further despite favourable North-North-Westerly boundary level wind direction. The highly favourable conditions for fire-related intrusion in Delhi is expected to continue," it said.

SAFAR predicted better ventilation for the next two days but said the AQI is likely to improve only marginally, depending on farm fires. It is set to deteriorate slightly on November 3, it said.

The city recorded an air quality index (AQI) of 370 at 3 pm. The 24-hour average AQI was 367 on Saturday. It was 374 on Friday, 395 on Thursday, 297 on Wednesday, 312 on Tuesday and 353 on Monday.

An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

Delhi records lowest temperature

New Delhi: The national capital recorded a minimum temperature of 11.4 degrees Celsius on Sunday, the lowest this season so far, according to IMD. Normally, the Safdarjung Observatory, which provides representative data for the city, records a minimum of 15 to 16 degrees Celsius in the first week of November. The mercury dips to 11-12 Celsius by last week of November, it said.

Kuldeep Srivastava, the head of the regional forecasting centre of IMD, said the absence of cloud cover was the major reason for the low minimum temperature.

Clouds trap some of the outgoing infrared radiation and radiate it back downward, warming the ground. Another reason is calm winds, which allow formation of mist and fog, Srivastava said.  There hasn't been much snowfall in the hills, so cold winds from that region are yet to start affecting Delhi's weather, he added.

The month of October was the coolest in 58 years in the national capital, according to IMD.

The mean minimum temperature in October this year was 17.2 degrees Celsius, the lowest since 1962, when it was 16.9 degrees Celsius, it said.

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