Delhi air improves, but respite will be short-lived

Delhi recorded an average air quality index (AQI) of 389, down from Sunday’s reading of 405, as per the Central Pollution Control Board’s daily bulletin at 4pm on Monday.

Delhi’s air improved marginally on Monday, dropping to the “very poor” category after three consecutive days of “severe” air, as wind speeds picked up over the Capital, allowing dispersal of pollutants post noon. Delhi recorded an average air quality index (AQI) of 389, down from Sunday’s reading of 405, as per the Central Pollution Control Board’s daily bulletin at 4pm.

A smog-engulfed view of construction near Parliament House in New Delhi on Monday. (Sanjeev Verma/HT PHOTO)

The respite is expected to be shortlived as agencies have forecast wind speeds to hover around 15-20km/hr range on Tuesday, after which calm wind conditions, which are not conducive to clearing the air, are expected to return from Wednesday.

Gufran Beig, founder and project director at the Centre-run System of Air Quality and Weather Forecasting And Research (SAFAR), said immediate relief is unlikely as the wind speed on Tuesday is not expected to be strong enough to improve the AQI beyond the “very poor” category.

“We had forecast wind speed to pick up on Monday and Tuesday but even when they touch 20 km/hr, it will still keep AQI within the ‘very poor’ category. By Wednesday, we will again have calm winds and AQI will start returning to the higher end of the ‘very poor’ category,” said Beig.

According to the Indian Meteorological Department (IMD), calm wind conditions were prevailing in Delhi till 10.30am, after which wind speed rose to 15km/hr during the afternoon.

“Wind speed ranged from 10-15km/hr during the day but calm wind conditions were back after 5pm. Delhi’s overall visibility ranged from 300 metres in the morning to 2,500 metres during the day, owing to smog,” said IMD scientist RK Jenamani.

In its forecast on Monday, the Early Warning System (EWS) for Delhi -- a forecasting mechanism under the Union ministry of earth sciences -- stated that air quality is unlikely to improve beyond the ‘very poor’ category, with calm or slow wind conditions, unfavourable for dispersion of pollutants, predicted at night time.

“Winds are likely to be relatively strong during Monday and Tuesday. On Wednesday, air quality is likely to deteriorate again due to calm winds, but it will remain in the ‘very poor’ category,” it said.

Meanwhile, Delhi recorded a maximum of 26.1 degrees Celsius (°C) on Monday, a degree above normal, and the minimum was 10.3°C, which is normal for this time of the season.

IMD has forecast the minimum temperature to drop to around 9°C on Tuesday but it is expected to increase to 12°C by Wednesday, under the influence of a western disturbance. “There is a possibility of very light rain occurring in parts of Delhi on Thursday. This western disturbance will raise the minimum temperature,” he said.