Noida, Ghaziabad most polluted, AQI plunges into severe

Two days after a slight improvement in air quality, Noida, Greater Noida and Ghaziabad slipped to “severe” levels once again on Tuesday

Two days after a slight improvement in air quality, Noida, Greater Noida and Ghaziabad slipped to “severe” levels once again on Tuesday.

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The three cities also emerged as the most polluted cities in the country, with Ghaziabad topping the air quality index (AQI) chart, followed by Greater Noida and Noida, respectively. This is the fifth time this year that the cities were breathing the worst air -- previously it was on January 1, 2, 15 and 17.

According to the Central Pollution Control Board (CPCB), Noida’s AQI, on a scale of 0 to 500, on Tuesday was 432 against 363 a day earlier. The AQI of Greater Noida was 434 against 360 or very-poor a day earlier. The AQI of Ghaziabad was 436 against 381 a day earlier.

An AQI between 101 and 200 is considered ‘moderate’, between 201 and 300 is ‘poor’, between 301 and 400 is considered ‘very-poor’ and above 400 is considered ‘severe’.

According to the weather department, the wind direction changed form easterly to westerly and north-westerly due to which the speed dropped leading to poor ventilation conditions.

“The wind speeds dropped almost to calms as the wind directions changed from comparatively warmer easterly to north-easterly and westerly. Whenever, the wind directions changes, the wind speed drops due to which the particle pollutants also increase and lead to spike in pollution levels,” said an official at India Meteorological Department (IMD).

According to the pollution monitoring agencies however, the air quality is likely to improve as the wind speed is likely to increase thereby improving the ventilation.

The major pollutant or PM2.5 in the region also spiked from three times the safety standards on Monday to five to six times higher than the standards.

The average PM2.5 for Noida on Tuesday was 334.71 microgrammes per cubic metres (µg/m3) against 220.43 µg/m3 on Monday. The average PM2.5 for Greater Noida was 314.38 µg/m3 against 232.86 µg/m3 a day earlier. The PM2.5 level for Ghaziabad was 346.63 µg/m3 against 220.11 µg/m3 a day earlier. The safe limit for PM2.5 is 60µg/m3.

According to the System of air quality and weather forecasting and research (SAFAR), the air quality is likely to improve slightly over next two days.

“Surface winds are north-easterly and low, Surface winds are forecasted to shift in direction from easterly to north-westerly and gain in speed. The ventilation coefficients are likely to improve significantly from tomorrow and AQI is likely to improve to the middle to lower end of Very Poor on 20th January. AQI is forecast to further improve to the lower end of the Very Poor to Poor category on 21st January. Marginal deterioration of AQI to Very Poor category is forecasted on 22nd January,” said SAFAR on Tuesday.

The weather department has forecasted that the temperature would drop by two to three degrees over the next two days due to the wind direction.

Dense fog conditions may, however, improve and increase visibility from around 50 metres in the morning to about 200 to 300 metres, especially around open areas and expressways.

According to the weather analysts, the wind speed is likely to increase over next two days and reach around 20 kmph by Thursday. This will lead to drop in the mercury and improve the visibility. “The cold waves will not return. The minimum and maximum temperatures may however drop below two degrees of the season’s average,” said Mahesh Palawat, vice president, meteorology and climate change, Skymet.

He added that the mercury may further drop and NCR may see slight drizzling around January 22 and 23 due to a western disturbance.

On Tuesday, the minimum temperature in Noida were recorded at 8.9 degrees Celsius against 9.7 degrees Celsius a day earlier. The maximum temperature for Noida was 20.5 degrees Celsius, against 20.1 degrees Celsius.

The average minimum and maximum for NCR, based on Safdarjung observatory was recorded at 6.9 degrees Celsius and 20.4 degrees Celsius, both one degrees below the season’s average.