AQI ‘severe’ for 3rd day, fails to improve despite forecast

The Capital recorded a third consecutive day of ‘severe’ air on Thursday, with AQI readings consistently above the 400 mark. This, despite the Centre’s Early Warning System (EWS) — the model that triggers Grap measures — forecasting ‘very poor’ air for Tuesday, Wednesday and Thursday, underscoring a widening gap between projections and actual pollution levels.

- Jasjeev Gandhiok

‘On Tuesday, despite an earlier EWS forecast that the AQI would stay in ‘very poor’, Delhi recorded the first ‘severe’ day of the season. Since then, it has stayed above 400 (‘severe’) for three days despite EWS's forecasts

According to the Central Pollution Control Board (CPCB), an AQI of above 400 falls under the ‘severe’ category. Between 301 and 400 is classified under ‘very poor’; 201-300 under ‘poor’; 10i-200 under ‘moderate’; and 51-100 under ‘satisfactory’

The EWS is operated by the Indian Institute of Tropical Meteorology (IIT-M), Pune, under the Union ministry of earth sciences. IIT-Malso manages the Decision Support System (DSS), which estimates the contribution of various sources, such as stubble burning and vehicular emissions, to Delhi's pollution. IIT-M officials did respond to HT’s requests for comment.

Experts said multiple factors may explain the gap between the projections and the current situation, including assumptions within the model that on-ground enforcement of antipollution measures would reduce pollution. On Tuesday, the Commission for Air Quality Management implemented Stage 3 measures, for AQI above 400, under its Graded Response Action Plan (GRAP).