Delhi’s air quality ‘very poor’ for 5th day; min temp 4 notches above normal

Calm winds continued to negatively impact the dispersion of pollutants keeping Delhi’s air quality in the higher end of the “very poor” category for a fifth straight day even as the minimum temperature was four notches above normal at 18°C.

The minimum temperature has risen after touching the season’s low of 16.5°C on November 3. It was 17.2°C on Wednesday and 17.6°C a day earlier. The maximum temperature was expected to hover around 33°C on Thursday compared to 32.3°C a day earlier.

At least nine stations recorded “severe” air quality at 9am on Thursday. Anand Vihar recorded an average Air Quality Index (AQI) of 427, followed by Wazirpur (424). An average AQI of 367 was overall recorded. This marked a marginal increase from Wednesday’s 4pm reading of 352.

AQI has been at the higher end of “very poor”—over 350—since November 3 when Delhi recorded its highest of the season at 382. It has been over 300 and in the “very poor category” since October 30. The air quality has not deteriorated to the “severe” zone so far despite unfavourable meteorological conditions. Delhi has previously recorded at least one “severe” air day by November 5 as per CPCB data available since 2015.

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

The wind conditions were expected to be unfavourable for the dispersion of pollutants until the weekend. The air quality was likely to remain “very poor” until Saturday.

A minimum visibility of 1,200 metres was recorded at Palam at 6:30am on Thursday. The visibility dipped to 800 metres across the city on Wednesday. Visibility below 1,000 metres is classified as fog.

The wind direction continued to oscillate between southeasterly and westerly. The contribution of stubble burning to Delhi’s PM 2.5—predominantly through northwesterly to westerly winds— was 20.3% on Tuesday, data from the Decision Support System calculated based on the actual fire counts showed. It was 23.3% a day earlier. On November 1, farm fires were estimated to have contributed a season-high of 35.1% of Delhi’s PM 2.5 load.