Another hazy in Delhi, AQI dips further

New Delhi: A layer of smog shot down visibility on Friday as the air remained dense with pollutants, with unfavourable weather conditions keeping the air quality index (AQI) dangerously close to the “severe” category, weather officials said.
While the 24-hour average AQI on Friday was recorded at 380 (very poor) at 4pm, according to the Central Pollution Control Board’s (CPCB), multiple air quality monitoring stations showed readings that breached the 400-mark.
Of the 32 air monitoring stations that were used to calculate the average AQI, 17 recorded “severe” air levels at 11am, which increased to 18 at 12pm. Delhi’s average AQI at 11am was recorded at 390.
However, by 4pm, the total number of stations in the “severe” air zone came down to 12, improving the average for the city. The reading was still worse than a day ago, when AQI was 377 (very poor), while on Wednesday, it was 352 (very poor).
Meanwhile, PM2.5 remained the major pollutant in the air, according to CPCB.
Forecasts show that the air quality is likely to stay in the “very poor” category till at least Monday.
CPCB 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 Capital also recorded fog conditions, as visibility at the Safdarjung weather station dropped to 800 metres for a fourth day in a row at around 9.30am. It improved over the day, the India Meteorological Department (IMD) said. According to weather experts, it is officially called a fog when visibility drops below 1,000 metres.
Combined with pollutants, “smog condition with predominant surface wind from variable directions with wind speed reaching 4-6kmph prevailed during daytime on Friday”, the weather office said .
Experts attributed this to low wind speeds that stop the dispersal of pollutants.
“The average wind speed over Delhi over the last three days did not exceed 2m/s, and this unfavourable meteorology has been hampering the dispersion of pollutants, leading to AQI in the upper levels of very poor,” said Priyanka Singh, programme lead ,Council on Energy, Environment and Water.
Meanwhile, the contribution of stubble burning, which had been over 20% from Monday to Wednesday, went down by a couple notches on Thursday to 17.81%, according to the Decision Support System (DSS).
“The factors driving poor quality over Delhi currently include stubble burning in the upwind states of Haryana and Punjab. Local pollution sources like transportation and dust have also played a major role. Further, citizens should avoid exposure to air pollution by reducing outdoor activities and wearing masks,” Singh added.
According to the Air Quality Early Warning System (AQEWS) for Delhi, the predominant surface wind on Delhi had been coming from variable directions on Friday. Smog or shallow fog is also likely on Saturday morning, it predicted.
AQEWS added, “The outlook for subsequent six days is that the air quality is likely to be in very poor category.”
Delhi recorded yet another warm day on Friday, as the maximum temperature was 31.7 degrees Celsius (°C) — two degrees above the normal for this time of the year, and same as the day before. The minimum stood at 18.1°C, four degrees above normal and 0.1°C higher than the previous day’s low of 18°C. Forecasts show the maximum and minimum temperatures are likely to hover around 32°C and 18°C, respectively, on Saturday.