Air quality likely to improve but only temporarily

According to the Central Pollution Control Board (CPCB) data, Delhi’s overall air quality index on Monday was 353, in the ‘very poor’ category. This was slightly above Sunday’s reading of 349, also in the ‘very poor’ range.

Delhi’s air quality may improve slightly, mostly due to meteorological factors, on Tuesday after remaining in the very poor zone for four consecutive days. According to the forecast by India Meteorological Department (IMD), while pollution levels showed a marginal spike on Monday, wind speeds improved through the day and its impact is likely to be experienced by Tuesday.

On Monday, this limit was around 3500 metres, which gave ample space for the pollutants to mix with the atmosphere instead of getting trapped closer to the ground. (HT Photo)

According to the Central Pollution Control Board (CPCB) data, Delhi’s overall air quality index on Monday was 353, in the ‘very poor’ category. This was slightly above Sunday’s reading of 349, also in the ‘very poor’ range.

“The pollution load was lower today as compared to the last few days and the wind speed improved from 6kmph to 12 kmph during the day. Since the CPCB’s evening bulletin is a 24 hour-average AQI figure, we will be able to see the impact of the winds from Tuesday,” said Vijay Soni, head of IMD’s Environment Monitoring Research Centre.

Soni said along with the wind speed, an improvement in the mixing height also helped better dispersion of pollution particles on Monday. The mixing height is the height of vertical mixing of air and suspended particles above the ground.

This height is primarily determined by temperature. When the temperature in the city increases, the air expands and pushes the height up, giving pollutants closer to the ground more space to mix with the atmosphere. On Monday, this limit was around 3500 metres, which gave ample space for the pollutants to mix with the atmosphere instead of getting trapped closer to the ground.

The improvement in the air quality will, however, be temporary. Scientists said that from October 28, the AQI will be pushed back to the ‘very poor’ range and it will remain in the danger zone till the end of the month.

IMD forecast said that the wind direction over Delhi will continue to remain north-westerly through the week, which will transport smoke from stubble burning from the neighbouring states of Punjab and Haryana.

Union ministry of earth sciences air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (Safar) analysis also suggests that stubble burning continued to contribute to Delhi’s foul air on Monday.

“Safar synergized stubble fire counts again increased to 1,275 on Sunday. The Safar model estimate of stubble burning share in PM2.5 (ultrafine particulate matter with diameter less than 2.5 micrometres) is 16% for Monday. While the expected slight increase in local surface wind speed is a positive sign for Tuesday, improved winds speed is not forecasted to stay longer,” Safar air quality analysis read.