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Wind speed cleans ‘severe’ Delhi air, Saturday will be windy too

On Thursday, the average AQI had hit 469, more than a 100 points higher than the 359 on Wednesday. An AQI value above 400 on a scale of 500 is considered “severe”.

delhi Updated: Dec 22, 2017 21:53 IST
HT Correspondent
HT Correspondent
Hindustan Times
delhi,delhi news,air
On Thursday, the average AQI had hit 469, more than a 100 points higher than the 359 on Wednesday. An AQI value above 400 on a scale of 500 is considered “severe”.(Burhaan Kinu/HT PHOTO)

Delhi air on Friday cleaned up quite a bit from Thursday’s ‘severe’ levels because of the increase in wind speed.

Friday’s average air quality index clocked 336, which falls under the ‘very poor’ category.

On Thursday, the average AQI had hit 469, more than a 100 points higher than the 359 on Wednesday. An AQI value above 400 on a scale of 500 is considered “severe”.

The levels of PM10 and PM2.5, too, saw substantial decrease throughout the day. While PM10 concentration went down from 391.3μg/m3 at 6am to 288.2μg/m3 at 6pm, the level of PM2.5 saw decrease from 241.4.8μg/m3 at 6am to 169.6μg/m3 at 6pm.

Both PM10 and PM2.5 are ultra fine particles, the dominant pollutants in Delhi. The acceptable levels of PM10, the larger particulate matter, and PM 2.5, which measures the finer and more dangerous particulate matter, are 100μg/m3 and 60μg/m3, respectively.

Met officials said this comparatively cleaner air was because of high wind speed. “Westerly winds were blowing all day on Friday with a speed of 25km per hour. This improvement started from Thursday evening with wind speed reaching 15km per hour. This has improved the air quality substantially,” Kuldeep Srivastava, a senior Met department scientist, said.

The wind speed is expected to be high even on Saturday, which means less pollution, he said.

A thick smog enveloped the Capital on Friday with the mercury settling at 25.3 degrees Celsius, four notches above the season’s average. The minimum temperature was recorded at 11 degrees Celsius, three notches above the season’s average.

On Saturday, mainly clear sky is expected while mist or shallow fog is expected in the morning. The maximum and minimum temperatures would be around 25 and 10 degrees celsius, respectively.

“There will be shallow fog in the morning. The visibility in the early hours will remain around 500-600m. However, on Sunday morning, there might be moderate to dense fog,” a Met official said.

First Published: Dec 22, 2017 21:50 IST