A first: Delhi gets pilot study to analyse and forecast fog

In a brainstorming session at the Ministry of Earth Sciences, India Meteorological Department (IMD) DG Dr L S Rathore said, “The magnitude of socioeconomic problems associated with fog is only increasing… We started issuing our first fog forecasts in 2008 and have improved our accuracy… but are not able to interpret fog for the power sector and surface transport like railways and road.” The association of fog with high disease in crops would also be studied, he added. “This initiative is aimed at improving observational data networks of fog, and to predict its intensity within a 2-3 hour time line to help us reduce flight diversions and delays to a bare minimum.”

Scientists from different institutions met at IITM in August to study fog. At the next meeting in September, it was decided that the monitoring would begin this year. After field studies over six sites in Delhi to identify a suitable area to set up monitoring instruments, the Pusa institute campus and IGI airport were selected.

Dr G S Bhat from the Indian Institute of Science, Bangalore, and the chairperson of the joint Delhi 2015 fog campaign, said scientists had set up a 20-metre tower at IGI airport with high quality instruments which would monitor real-time data to understand fog. “The formation of smog with smoke or aerosols in the air along with fog, which reduce visibility, will also be studied in depth. We will be looking at the microphysics of fog, the land and weather phenomenon which instill its formation and the role of pollutants in the Indo-Gangetic Plain,” he said.

Dr R K Jenamani, head of airport Met office, said, “Fog is infinitely more complicated than a phenomenon like rainfall. Within a day, we do not understand properly why pockets have more intensity… some runways suffer more. While we can predict the onset of fog, we still cannot not accurately predict its intensity and exactly when it will withdraw, as we saw this Saturday.”

Dr Jenamani said the campaign would especially look at dust particles. “We need to study exactly how pollutants influence the number and size of fog droplets, thus also affecting the life cycle of the fog.” Experts said instruments set up at IGI would monitor chemical composition of particulate matter at different heights to analyse the role of pollutants in fog formation.

Dr Gufran Beig, project in-charge of SAFAR, said, “Our air quality analysis in the peak fog days in the winter months shows dense fog days are characterised by very high particulate matter level, which includes both PM 10 and PM 2.5.”