Delhi air quality remains poor for fifth consecutive day on Sunday

Air quality in the capital worsens every year October onwards due to various factors, including a drop in temperature, change in wind speeds and direction, and smoke from stubble burning in neighbouring states

Despite a forecast of marginal improvement, Delhi’s air quality continued to remain in the ‘poor’ zone on the fifth consecutive day on Sunday morning. The air quality index (AQI) was at 220, as per Central Pollution Control Board (CPCB) data at 8 am; hardly a drop from Saturday when the 24-hour average at 221.

The average AQI has been in the poor zone since Wednesday, when air quality plunged into the ‘poor’ zone for the first time since June 28. (PTI file)

Air quality enters the poor zone between 201-300 mark. Delhi’s average AQI has been in the poor zone since Wednesday, for the first time since June 28.

The System of Air Quality and Weather Forecasting and Research (SAFAR), the Central government’s air quality monitoring and forecast wing, had said that AQI could see a slight improvement on October 11 and 12.

“AQI is forecasted to marginally improve to the moderate category for Saturday; further AQI is forecasted to improve by October 12, but in the moderate category. The low pressure formed over the Bay of Bengal is likely to intensify to depression and move west northwestwards and influence the circulations in North and central India. A shift in Delhi surface wind direction, northwesterly to southeasterly by October 12 is forecasted. This could influence air quality positively in the coming week. Stubble burning fires observed Friday around Punjab, Haryana, and neighboring border regions with SAFAR synergized fire count estimated as 253 on October 10 but with marginal impact in Delhi AQI,” it said.

Air quality in the capital worsens every year from October due to various factors, including a drop in temperature, change in wind speeds and direction, and smoke from stubble burning in neighbouring states of Haryana and Punjab, and local sources of pollution.

Experts note that though faster winds play a major role in dispersing pollutants, they are not strong enough through the day to help Delhi currently.

Scientists at the India Meteorological Department said that even though the average wind speed is 15-16 kmph during the day, the north-westerly winds bringing in fumes from stubble burning of crops in Haryana and Punjab are adding pollutants in the atmosphere to the northwestern region, including Delhi-NCR. However, the wind speed is low from evening to morning -- thus, not allowing dispersion of pollutants -- and a drop in night temperature permits the pollutants to settle in the atmosphere.

“The air quality may improve slightly on October 11-12 because of thunderous developments likely in the region. The wind direction will also change to southeasterly during this time. However, this pattern will again change from October 15, with a return of northwesterlies and a dip in both night and day temperatures,” said an IMD scientist, adding that a significant deterioration in air quality is not likely in the next 10 days.

On Saturday, the minimum temperature settled at 21.5 degrees C, one notch below normal while the maximum temperature was at 35.2 degrees C, a notch above normal.