Delhi's air quality inches closer to 'severe' zone, AQI stands at 381

A thick blanket of smog covered the India Gate due to air pollution in New Delhi

Delhi's air quality was in the upper end of the very poor category Wednesday morning, while pollution levels have already entered the severe zone in the neighbouring cities of Ghaziabad and Greater Noida.

The city's air quality index (AQI) was 381 at 9 am. The 24-hour average was 367 on Tuesday. It was 318 on Monday and 268 on Sunday.

Ghaziabad and Greater Noida recorded an AQI of 430 and 410, respectively.

An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".

The maximum wind speed is expected to be 12 kmph on Wednesday, according to the India Meteorological Department (IMD).

The minimum temperature was 8.2 degrees Celsius on Wednesday and the maximum is expected to settle around 27 degrees Celsius, the weather department said.

The minimum temperature this season has remained 2-3 degrees Celsius below normal in the absence of a cloud cover on most days, according to IMD officials.

Clouds trap some of the outgoing infrared radiation andradiate it back downward, warming the ground.

The predominant wind direction remained westerly-north-westerly on most of the days. These winds blow from snowcapped western Himalayas towards the plains.

Another reason for the below normal temperatures is La Nina, a phenomenon associated with the cooling of Pacific waters and an antithesis to El Nino.

Calm winds and low temperatures trap pollutants close to the ground, while favourable wind speed helps in their dispersion.

The central government's Air Quality Early Warning System for Delhi said the air quality is likely to remain in the upper end of the "very poor" category due to unfavourable meteorologicalconditions.

There is a possibility of the air quality reaching the "severe" category between December 4 and December 7, it said.

The city's ventilation index -- a product of mixing depth and average wind speed was 2,500 m2/s on Tuesday and is likely to be 6,000 m2/s on Wednesday.

Mixing depth is the vertical height in which pollutants are suspended in the air. It reduces on cold days with calm wind speed.

A ventilation index lower than 6,000 sqm/second, with the average wind speed less than 10 kmph, is unfavourable for dispersal of pollutants.

The contribution of stubble burning in the neighbouring states to Delhi's PM 2.5 levels was 4 per cent on Tuesday, 7 per cent on Monday and 6 per cent on Sunday, according to the Ministry of Earth Sciences' air quality monitor, SAFAR.

(Only the headline and picture of this report may have been reworked by the Business Standard staff; the rest of the content is auto-generated from a syndicated feed.)

Dear Reader,

Business Standard has always strived hard to provide up-to-date information and commentary on developments that are of interest to you and have wider political and economic implications for the country and the world. Your encouragement and constant feedback on how to improve our offering have only made our resolve and commitment to these ideals stronger. Even during these difficult times arising out of Covid-19, we continue to remain committed to keeping you informed and updated with credible news, authoritative views and incisive commentary on topical issues of relevance.

We, however, have a request.

As we battle the economic impact of the pandemic, we need your support even more, so that we can continue to offer you more quality content. Our subscription model has seen an encouraging response from many of you, who have subscribed to our online content. More subscription to our online content can only help us achieve the goals of offering you even better and more relevant content. We believe in free, fair and credible journalism. Your support through more subscriptions can help us practise the journalism to which we are committed.

Support quality journalism and subscribe to Business Standard.

Digital Editor

Business Standard is now on Telegram.
For insightful reports and views on business, markets, politics and other issues, subscribe to our official Telegram channel