Delhi’s AQI worsens by 150 points in 24 hours; back to poor

The Capital’s tryst with “moderate” air was disrupted on Saturday even as the strong north-western surface winds that swept the city for five consecutive days came to a halt — considerably worsening the 24-hour average air quality index (AQI) reading by a whopping 150 points.

AQI on Saturday dropped to the dirtier end of the “poor” zone at 3pm with a reading of 287, further deteriorating to 309 (very poor) by 7pm. The average AQI was recorded at 295 (poor) at 4pm, according to the Central Pollution Control Board’s national bulletin. It was 145 (moderate) at the same time on Friday.

Meanwhile, isolated areas in the city recorded “cold wave” conditions as the minimum temperature dropped to 5.2 degrees Celsius (°C) at Safdarjung — representative of Delhi’s weather — which was five degrees below normal, the India Meteorological Department (IMD) said. IMD classifies it as a “cold wave” when the minimum is 4.5°C or more below normal. The minimum was 6.8°C a day before.

Forecasts by the Early Warning System (EWS) for Delhi, an air quality forecasting model under the ministry of earth sciences, showed the AQI would remain “very poor” till February 13.

The maximum was 23.6°C compared to 24°C on Friday. IMD officials attributed the wide difference between the maximum and minimum to the clear skies prevalent throughout the day.

“Delhi experienced clear skies throughout Saturday with no surface winds, leading to a lower minimum,” said Kuldeep Srivastava, scientist at IMD.

Srivastava added that some mist might be recorded on Sunday but skies will remain mostly clear. “The minimum should stay around 7°C for the next two days and the maximum is expected to stay around 25°C,” he added.

Some individual weather stations recorded a higher minimum on Saturday — Palam recorded a minimum of 8.2°C, Pitampura 10.2°C and Raj Ghat 9.4°C. The maximum in these stations were 22.1°C, 23.9°C and 22.4°C, respectively.