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Tuesday, Dec 10, 2019

We cant change meteorology, we need to curb emissions: Forecast scientist

cities Updated: Nov 15, 2019 21:32 IST
Jayashree Nandi
Jayashree Nandi
Hindustantimes
         

New Delhi

As Delhi gasps for breath under a spell of severe air pollution, an early warning system — developed by the Union ministry of earth sciences — has been helping scientists accurately determine causes of foul air and take effective steps to check it.

The early warning system, which has been functioning for a year now, sends inputs to agencies about an estimate of PM 2.5 (fine, respirable pollution particles) pollution from biomass burning, dust and also an indication if it’s from local emission sources.

Last month, the model’s resolution was scaled down from 2km to 400metres, helping it pick up sources and transport of air pollution more accurately.

The early warning system uses a WRF-Chem model (weather and chemical transport of pollutants) which can assimilate fire counts, weather data, aerosol optical depth (an indirect proxy for air quality, which shows how solid and liquid particles in polluted air block sunlight and lead to smog) to produce a three day forecast for air quality.

For example, the warning system gave a forecast of three “severe” days on November 10, on the basis of which the Supreme Court-mandated environment pollution control authority extended the severe category interventions like shutting schools, stopping all construction work, prohibition on use of diesel gen sets and introduction of odd and even scheme.

The forecast model showed a layer of smoke over Delhi-NCR and other neighbouring areas on Friday afternoon, when this HT reporter visited a mini air quality forecast control room at India Meteorological Department. The apportionment data on Friday estimated that biomass burning was contributing only 10 micrograms per cubic metres to the PM 2.5 concentrations of Delhi, while contribution from dust was nearly zero.

“We are seeing a declining trend in crop fires now. But whatever has accumulated hasn’t dispersed. The fresh emissions from biomass fires may be less today but pollutants have life. They can remain suspended. There were a large number of fires last week,” said VK Soni, senior scientist at IMD, who analyses modeling data released by the Indian Institute of Tropical Meteorology (IITM) Pune’s control room and briefs the Central Pollution Control Board (CPCB), Delhi Pollution Control Committee (DPCC) and the SC mandated Environment Pollution Control Authority (EPCA) everyday on air pollution outlook.

The model developed by Pune based Indian Institute of Tropical Meteorology (IITM) has the capability of apportioning other sources also. The team will consider dissecting those sources in future.

Soni, who has been seeing how pollutants travel from the northwest or the east to Delhi depending on the wind direction and accumulation of local pollutants over the region, doesn’t mince words about the crisis. “We cannot change meteorology. All we can do is to reduce pollution sources and emissions as much as possible,” he said.

He adds that agencies have so far promptly acted on his forecast for the past few months but pollution sources are innumerable.

The accumulation of smoke over Delhi is mainly a result of lack of wind, which picked up on Friday but not enough to disperse pollutants. “We have a wind speed of 8 to 10 kmph. Our model says it will rise 20 kmph on Saturday and that conditions will be favourable for dispersion.”