AQI in Delhi back to very poor as winds get slower

Temperatures increased marginally on the day and officials said they expect the mercury to remain stable till Monday.

Pollution levels in Delhi got worse on Friday as winds got slower, said the India Meteorological Department (IMD), even as the weather office predicted improved air quality over the weekend.

The average AQI in the national capital remains in the ‘very poor’ category, (File Photo / Representational Image)

Temperatures increased marginally on the day and officials said they expect the mercury to remain stable till Monday.

Recordings from the Central Pollution Control Board (CPCB) showed Delhi’s 24-hour average air quality index (AQI) at 4pm on Friday was 314 (very poor), worse than 289 (poor) a day earlier.

“The winds were relatively slower on Thursday, because of which there was some accumulation of pollutants in Delhi. But the winds picked up from Friday afternoon, the impact of which will be visible from Friday evening. There will be a marginal improvement in air quality on Saturday, and the AQI will remain in the poor range till November 13,” said VK Soni, head of IMD’s environment and research centre.

He said that winds will be strong enough to clear up pollutants till November 13, but added that the weather office expected the AQI to worsen into the ‘very poor’ zone again on November 14 and November 15, on the back of a fall in the temperature and wind speeds.

An AQI between zero 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.

“Low temperatures impact the mixing height of the atmosphere and force pollution particles to stay close to the surface,” explained Soni.

The air quality forecast issued by the Union ministry of earth sciences’ early warning system said the winds on Saturday are likely to get faster and reach 8-10kmph.

Meanwhile, the minimum temperature at Safdarjung, Delhi’s base station, was 9°C, up from 8.4°C on Wednesday. The maximum temperature was 23.7°C, a notch below normal.

“Temperatures are likely to remain in the 7-8°C range for the next two days. Cold winds from the freshly snowed states of Jammu & Kashmir, Himachal Pradesh and Uttarakhand will blow into Delhi and keep the temperatures lower compared to what it was in the first week of December,” said a senior Met official.