Delhi pollution: Despite light rain, air quality remains very poor

The Safdarjung observatory, which is considered representative of Delhi, received 0.8mm of rainfall till 8.30am on Monday, while Ayanagar received 1.2mm.

The air quality index (AQI) remained in the ‘very poor’ category -- increasing from 305 on Sunday to 322 on Monday, as per the Central Pollution Control Board’s daily bulletin -- despite light showers in the Capital early Monday morning.

Delhi recorded a maximum temperature of 24.8°C on Monday, one degree above normal, and the minimum was recorded at 15°C, six degrees above normal. (Arvind Yadav/HT Photo)

The Safdarjung observatory, which is considered representative of Delhi, received 0.8mm of rainfall till 8.30am on Monday, while Ayanagar received 1.2mm.

While an improvement in air quality is forecast in the next 24 hours, the IMD has also predicted a drop in temperatures, with the minimum expected to return to single digits by the weekend, and the maximum dropping to 21-22 degrees Celsius (°C) as cold north-westerly winds start blowing from Tuesday.

IMD scientist RK Jenamani said while the minimum temperature tends to rise under the influence of a western disturbance, wind direction will once again change to northwesterly from Monday night and Tuesday morning, bringing colder winds towards Delhi. “There has been snowfall in the higher ranges and these cold winds will now blow towards Delhi, bringing a drop in both minimum and maximum temperatures. We can expect cold day-time temperature by the end of the week too,” he said.

According to IMD’s seven-day forecast, Delhi’s minimum temperature will start hovering around 9-10°C range from Wednesday onwards, and the maximum temperature is expected to drop to 22°C by Sunday.

Gufran Beig, project director and founder at the Centre-run System of Air Quality and Weather Forecasting And Research (Safar), said wind speed will be good on Tuesday too, which will increase ventilation, but warned that the drop in temperatures will reduce the mixing height and have a negative impact on dispersal of pollutants.

“Wind speed will remain good but AQI may remain in the ‘very poor’ range for the next few days,” he said.

Tanushree Ganguly, programme lead at the Council on Energy, Environment and Water (CEEW), said as per forecasts, air quality could improve to the “poor” or “moderate” categories in the next two days as surface winds pick up.

“However, as we approach peak winter, minimum temperatures are likely to drop gradually leading to a more stable atmosphere and low mixing height. This will trap pollutants closer to the surface, resulting in ‘very poor’, and occasionally ‘severe’, air quality levels,” she said.

IMD’s forecast shows Delhi is expected to record shallow fog on Tuesday morning, with the maximum and minimum hovering around 24°C and 12°C, respectively.