The air quality index (AQI) in Delhi-NCR, which has been ranging in the ‘good’ to ‘satisfactory’ categories due to reduced emissions during the nationwide lockdown, saw a marginal rise on Monday. The AQI in Delhi went up from 102 at 4 p.m. on Sunday to 142 at the same time on Monday.

Sources at the Met department said that bursting of crackers on Sunday night may have caused the spike but the key factor was lowering of wind speed.

In response to Prime Minister Narendra Modi’s call of ‘9 p.m., 9 minutes’ to express resolve against COVID-19, Delhiites lit candles and diyas on Sunday, but some also burst crackers.

In Gurugram and Noida, where AQI was in the ‘satisfactory’ category on Sunday, the numbers went up to the ‘moderate’ category on Monday. The AQI in Gurugram and Noida was recorded at 91 and 84 on Saturday and 106 and 120 on Monday, respectively.

The rise in the AQI, according to scientists at the Central Pollution Control Board and SAFAR, was “purely temporary”. It has been attributed to the lowering of night-time inversion layer height with reduced windspeed rather than any appreciable changes in significantly reduced COVID-19 lockdown-related emissions.

“Rain is expected on April 7 [Tuesday] and forecasting model suggests the AQI is likely to improve and go back to the ‘satisfactory’ category with further improvement on April 8,” a bulletin by SAFAR read. The Met department has forecast gusty winds up to 30-40 kmph on April 7 with light rain and thundershowers.