Whole week of ‘very poor’ air for Delhi; low temperature plays significant role

The Capital’s air quality marginally deteriorated on Wednesday and clocked a 24-hour average air quality index of 378 (very poor) — the worst it has been in December — according to the Central Pollution Control Board’s (CPCB) national bulletin at 4pm.

Wednesday was also the seventh consecutive day when the city’s AQI remained in the “very poor” zone. The AQI at the same time on Tuesday was 355 (very poor).

Met officials said that the worsening air quality was aided by low temperatures and calm winds at night. However, wind speeds will likely pick up on Thursday to 20km/hour, preventing further deterioration, they added.

Before Wednesday, Delhi recorded its worst AQI in December this year on December 1 at 372 (very poor). The city is yet to log a “severe” air day this month and the last such day was on November 24, with an AQI of 415.

According to the Early Warning System for Delhi, the city’s AQI will likely remain in the “very poor” for the next three days (December 14-16). “Delhi’s air quality is likely to remain in the ‘very poor’ category from December 14 to 16. The outlook for the subsequent six days shows the air quality is likely to remain between ‘very poor’ to ‘poor’,” said EWS.

CPCB classifies an AQI of 51 to 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”.

According to officials, shallow fog was also recorded on Wednesday, with the lowest visibility recorded at around 600 metres. “The maximum wind speed was 8-10 km/hour during the day, but this will almost double, touching around 20 km/hour during the day on Thursday,” said, Kuldeep Srivastava, scientist at India Meteorological Department, adding that shallow fog will likely persist in the coming days as well.

Delhi’s minimum temperature, meanwhile, was recorded at 7.4 degrees Celsius (°C) on Wednesday — a degree below normal for this time of the year. It was 6.8°C a day earlier and was 6.5°C — the season’s lowest, on Monday. The minimum is forecast to be around 6°C on Thursday, oscillating between 6-7°C till Sunday.

The maximum temperature was recorded at a high 24.6°C – two notches above normal. It was 24.8°C a day earlier. The maximum is forecast to remain around 24°C till the weekend, meaning days will remain warmer than usual for this time of the year.