Delhi air quality unlikely to worsen in next two days; temperatures may dip

Delhi’s air quality, which was recorded to be 393 on the Air Quality Index on Thursday, improved to 370 on Friday.

The air quality in Delhi-NCR is unlikely to worsen and pollution levels may not slide back to the ‘severe’ category over the weekend, scientists managing the National Capital’s early warning system said on Friday.

Vehicles move through Delhi- Gurugram Expressway amid dense smog and with increasing air pollution, in Gurugram on October 29. (Yogendra Kumar/HT PHOTO)

Instead, the mercury could register a dip over the next few days and drop to around 13 degrees Celsius on Diwali day on account of a western disturbance which has triggered snowfall in the high altitudes of Himachal Pradesh and Jammu and Kashmir. Cold northwesterly winds could start blowing from Sunday.

The Air Quality Index (AQI) value of Delhi, which came in at 393 on Thursday, improved to 370 on Friday. On a scale of 0-500, an AQI value of 301-400 is considered ‘very poor’ and a value above 400 is considered ‘severe’.

Delhi had been reeling under ‘very poor’ quality of air since October 24, except for Tuesday when it hit a season’s high of 401 and breached the ‘severe’ level for just a day.

“The air quality could see some improvement on Saturday. It will again deteriorate on Sunday. However, it is unlikely to slide back to severe levels. Instead we expect the air quality to remain in the very poor category with AQI levels ranging between 301 and 400,” said one of the scientists cited above who asked not to be named.

According to experts, Delhi-NCR needs a wind speed of more than 10 km per hour and a ventilation index (which determines how fast pollutants get dispersed) of at least 6,000 square metres/second.

Anything below this will fail to disperse the pollutants and pollution levels will rise.

Read: Ban on private vehicles, odd-even scheme likely if Delhi continues to choke

“On Saturday, we will have the required wind speed and ventilation index because of which Delhi could see some improvement in air quality. Conditions are, however, likely to worsen again on Sunday as the ventilation index is likely to drop to around 4,000 square metres/second,” the scientist added.

On Friday, the maximum and minimum temperatures were 31.6 and 16 degrees Celsius respectively.

“With snowfall in the hills because of a westerly disturbance, and northwesterly winds expected to flow in from Sunday, the temperature could dip over the next few days. It could drop to around 13 degrees on November 7,” said an IMD official who asked not to be named.

The levels of particulate matter, the primary pollutants in Delhi’s air, which had shot up to four times the safe limits on Thursday because of unfavourable weather conditions, also improved on Friday.

Read: Delhi civic bodies intensify drive against pollution, impose Rs 30 lakh in fine