Delhi’s early warning system neither quick nor right | Latest News Delhi

Developed by the Indian Institute of Tropical Meteorology (IITM) as a tool to predict when Delhi’s air could turn foul, the EWS is meant to be the basis for how pollution-control measures are activated.

That it failed to predict the rapid deterioration of the Capital’s air on Thursday by a margin of whopping four days means the city is virtually no more prepared than it was in recent years, when the response to the crisis had mostly been reactive and ineffective.

The EWS provides a daily assessment of how the air quality will be for the nine days, with the model calibrating its predictions every 24 hours. Its forecasts are the basis for how the graded response action plan (Grap) is activated with the understanding that the sooner polluting activities are stopped, the more effective these steps would be.

This lack of advanced warning meant that even the Commission for Air Quality Management’s subcommittee on Grap was caught unawares, convening hurriedly at 4.30 pm on Thursday as the haze kept thickening over the Capital, with pollution levels steadily climbing. By this time, the AQI had already reached 392, from 364 at 4pm a day before.

“The whole idea behind revising Grap was to make it pre-emptive. Earlier, we would wait for the air quality to touch a certain mark, before the measures were imposed. Now, we need not do that and can do it based on forecasts, but these need to be accurate too,” said Sunil Dahiya, analyst at the Centre for Research on Energy and Clean Air (CREA).

In its forecast issued on Thursday morning, the model said the severe pollution level would be breached between November 6 and 11. “Delhi’s air quality is likely to be in the ‘very poor’ category from November 3 to 5. The outlook for the subsequent six days shows air quality is likely to remain in ‘very poor’ to ‘severe’ category,” said Thursday’s EWS forecast.

Mukesh Khare, professor at IIT Delhi and a former member of CAQM, said such anomalies either point to an outdated emissions inventory – or the need to recalibrate the model.

“It may largely be down to some variations in the emissions inventory, which is a long-term database of emissions that each sector contributes. It is important to update this inventory every two years and if that is not done, estimates by the model may not be able to give an accurate forecast,” he said, stating he had made a recommendation to the Central Pollution Control Board (CPCB), as a CAQM member, asking for a uniform protocol in calculating an emissions inventory.

“So far, agencies and states are also calculating this inventory in their own way – without a fixed protocol,” he added.

Emissions inventories are an estimation of what source contributes to how much pollution.

The EWS’s forecasts utilise two modelling frameworks — one based on National Center for Atmospheric Research’s (NCAR) atmospheric chemistry transport model and the second one based on a Finnish Meteorological Institute model. Both models are combined and have a data assimilation facility, which is fed information from satellites on dust aerosols, particulate matter from stubble burning and other air pollutants such as SO2 and NO2.

The models also take into account background aerosols and pollutants, long range transport of dust from dust storms, and particulate matter from farm fires.

EWS is part of the ministry of earth sciences, but is executed by IITM, in collaboration with the India Meteorological Department. HT did not receive a response from any of these agencies despite queries about the inaccurate forecast.

Last month, the EWS was among three agencies that are meant to provide a sense of what is causing pollution in the Capital but were all taken offline briefly over what the government said was a need to standardise the forecasting since the models used different nomenclature.

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