Delhi’s air slightly better but remains very poor

Strong surface winds continued to offer some relief to Delhi residents from the onslaught of post-Diwali pollution as the city’s air saw marginal improvement where it stayed in the “very poor” category on Saturday.
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However, according to forecasts by the Air Quality Early Warning System (AQEWS) the air quality will stay in the “very poor” category at least till Tuesday.
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Delhi’s 24-hour average air quality index (AQI) stood at 316 (very poor) at 4pm, a slight improvement from 339 (very poor) recorded at the same time on Friday, according to the Central Pollution Control Board’s (CPCB) national bulletin. However, by nightfall, AQI had again started rising, and was 354 at 10pm on Saturday.
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“The air quality is likely to be in very poor category from Sunday to Tuesday. The outlook for the following six days is that the air quality is likely to be in very poor category,” the AQEWS bulletin said on Saturday.
AQI at 4pm before Diwali celebrations began on Thursday was 328, and held steady till 9pm after which it began steadily worsening — 330 at 10pm, 338 at midnight, 347 at 3am and 362 at 9am, before it began improving again — primarily due to strong surface winds of 10-15 km/hr and higher than normal temperature for this time of the year. AQI was 354 at noon on Friday, 339 at 4pm, 314 at 10 pm, and 291 at 8am on Saturday, before the air quality dipped again.
Experts said that strong winds came to Delhi’s rescue, allowing simultaneous dispersion of pollutants. However, the winds are expected to become comparatively calm starting Sunday.
“We had steady winds throughout Diwali day and on Friday, too. Wind speed was 12-16 km/hr till 6 pm on Thursday. It dipped marginally, but remained between 3 and 7 km/hr through the night and again picked up to around 10 km/hr when the sun came out on Friday, aiding the improvement,” said an India Meteorological Department official, who asked not to be named.
Mahesh Palawat, vice president at Skymet meteorology believes the improvement is likely to be short lived, with winds to once again become calm on Sunday.
“Until we have these winds, AQI should benefit but by Sunday, we are expecting calm winds again and local pollutants will once again start to accumulate. However, the wind speed might start picking up from November 5 again, thus reducing pollution,” he said.
Palawat added that the wind direction is also expected to change from north westerlies, as was observed on Saturday (with speed 8-10kmph), to calm south-easterlies.
The Central Pollution Control Board (CPCB) classifies AQI between 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”.
Meanwhile, Delhi’s minimum temperature went down slightly. The minimum on Saturday was recorded at 17.1 degrees Celsius (°C), two degrees above normal, as compared to 18.4 °C a day before. The maximum temperature, however, barely changed and was logged at 33.9 °C, three degrees above the normal. It was 33.6 °C on Friday.
According to the India Meteorological Department, the minimum temperature is expected to stay between 16-17°C in the upcoming week, while the maximum is forecast to oscillate between 32 °C and 33 °C.