AQI improves slightly in Delhi, but may worsen again

The pollution in the upper reaches of the “very poor” zone is still way above the safe limits, and exposes residents to a range of severe ailments.

The national capital’s pollution levels on Monday improved marginally to “very poor” after three straight days in the “severe” zone of the air quality index (AQI).

Mayur Vihar Phase 3 on a cold and smoggy Monday morning in New Delhi. (Sunil Ghosh/HT Photo)

Delhi clocked a 24-hour average AQI of 383 on Monday, as against 411 on Sunday.

To be sure, the pollution in the upper reaches of the “very poor” zone is still way above the safe limits, and exposes residents to a range of severe cardiac and respiratory ailments.

The AQI was 450 on Saturday, and 409 on Friday.

Cities across the National Capital Region (NCR) saw a similar drop in pollution. Noida’s AQI improved from 368 to 316, Gurugram’s dipped from 304 to 298, Greater Noida’s improved from 376 to 336 and Ghaziabad’s from 360 to 280.

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According to the Central Pollution Control Board’s (CPCB) forecast, Delhi’s AQI will remain “very poor” on Tuesday, before worsening again a day later. “The air quality is likely to deteriorate again from December 27 as meteorological conditions are extremely unfavourable,” said the early warning system’s air quality and weather bulletin.

CPCB classifies an AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.

Meanwhile, Delhi on Monday recorded a minimum temperature of 7.8 degrees Celsius (°C), which is around normal for this time of the year, and a marginal rise from the 7.6°C on Sunday.

Delhi’s mercury fell to a low of 4.9°C on December 15, but has largely been above that mark since then.

On Monday, Delhi recorded a high of 23.6°C, which is three notches above normal for this time of the year, but two degrees below the 25.9°C on Sunday.

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The wind speed was 8-10kmph, around the same as the 8kmph on Sunday. Officials said that it was expected to be similar on Tuesday.

“The predominant wind is from the northwest direction with an average wind speed of 8-10kmph, which is not likely to affect the temperature,” said Kuldeep Srivastava, scientist at the India Meteorological Department (IMD).

Dipping day-time temperatures and, consequently, a narrower gap between the maximum and minimum temperature are a more accurate bellwether of the winter’s spread than the night-time value alone.