Delhi: AQI improves slightly to ‘very poor’ category, thanks to mild surface winds

An increase in surface winds through the day on Monday helped bring down the average 24-hour air quality index (AQI) in Delhi within the ‘very poor’ category on Tuesday, five consecutive days after hovering under ‘severe’.

The recording stations clocked an average AQI of 395 (very poor) at 7 am today as compared to 421 (severe) at 4 pm on Monday. Along with surface winds, a host of restrictions under stage 4 of the Graded Response Action Plan (GRAP) a day earlier acted as a fillip to the slightly improved air quality situation in the national capital.

Delhi is likely to see wind speeds of 8-10kmph today afternoon as well, which should further aid in the dispersion of pollutants, officials said.

An IMD official said the wind direction, which had been northwesterly so far, switched to southeasterly on Monday, with a western disturbance to influence northwest India between November 7-10. “This will largely influence Jammu and Kashmir, but some impact is expected in Delhi too, as the wind direction will become variable and we expect wind speeds to pick up gradually from Tuesday afternoon,” said Kuldeep Srivastava, scientist at IMD.

“The wind speed is expected to gradually increase from around 8kmph on Tuesday, all the way up to an average wind speed of 15kmph by November 11,” he added.

Real-time IMD data showed visibility had also improved in comparison to previous days, with it recorded at around 1,100 metres at 7 am this morning. It was at 400 metres at the same time on Monday.

Delhi’s AQI recorded a high of 454 at 4 pm on Sunday, prompting the Commission for Air Quality Management (CAQM) to invoke stage 4 of GRAP the very day. Curbs under stage 4 focus heavily on diesel vehicles and bans all diesel light commercial vehicles that are registered outside Delhi, and are non-BS-VI, from entering the capital.

Similarly, there is a ban on entry of trucks into Delhi, alongside a curb on the plying of all diesel-Medium Goods Vehicles (MGV) and heavy goods vehicles (HGV) in the capital. Under this category, all linear construction projects such as highways, roads and flyovers have also been stopped.

The AQI crossed 400 for the first time this season last Thursday and remained ‘severe’ since 5 pm till now.

On Monday, the Delhi government re-imposed the odd-even scheme from November 13-20 in a bid to prevent further deterioration, especially after Diwali on November 12. Chief minister Arvind Kejriwal convened an emergency-meeting yesterday, after which Delhi environment minister announced that they had decided to not only implement odd-even again but have also directed schools to suspend physical classes for all grades barring classes 10 and 12, until November 10. Classes can be held online during this period, he said. A decision to allow 50% government employees to work from home will be taken later.