The Indian Institute of Tropical Meteorology (IITM) has developed an early warning and forecasting system that for the first time takes into account the role of pollution in creating fog and poor visibility in the Delhi-NCR during winter, senior scientists said Thursday.

They said the new system will not only help Delhi prepare for foggy conditions, it will also allow agencies to avoid flight delays and cancellations while providing forecasts for public consumption.

The fog forecasting system, now tentatively implemented by IITM in collaboration with the UK Met office, will predict the fog and visibility status in the Indo-Gangetic Plains (IGP) in advance, while also providing a clear picture of how aerosols are trapped in the Atmosphere affect fog and visibility.

Currently, the system gives predictions two days in advance, but the technology is being studied and necessary changes will be made in the coming weeks before the portal is released, scientists said.

“As part of the project initiated by the Union’s Ministry of Earth Sciences, we worked intensively on understanding the fog in Delhi almost three to four years ago. Based on our knowledge and learning, we introduced the fog forecast system on a pilot basis. This will not only help the authorities prepare for the heavy foggy spells that Delhi experiences in December and January, but also make these conditions available for public consumption, ”said Sachin Ghude, researcher at IITM Pune who is also the director the government department’s Winter Fog Experiment (WiFEX).

The site will, through various graphic representations, give a clear picture of the visibility the city is likely to see at any time of the day, the possibility of dense fog (visibility less than 200 meters), the presence of dust in the air, the size of dust particles and theirs Influence on vision.

For example, on December 17th, the fog forecast said that morning visibility in Delhi will likely be over 2,000 meters and will steadily improve as the day progresses.

Gaurav Govardhan, a scientist at IITM who is also part of the team that developed the system, said aerosols, or pollutants, are known to increase the formation of mist droplets.

“The technology is the same as for the general weather forecast – only this time we take into account the influence of aerosols or pollutants on the formation of fog. Aerosols can help in the formation of mist droplets, which essentially means that the more pollutants there are in the air, the more likely it is that mist droplets will form. You don’t need very humid air for fog. If aerosols are present in the air, less humid air can also encourage fog formation, ”said Govardhan.

In November and early December, when temperatures were still above normal, there was a smog episode (fog in connection with pollutants) in Delhi, which reduced visibility at both city airports – Safdarjung and Palam – to 200 to 500 meters. According to scientists from the India Meteorological Department (IMD), this was a result of the increased pollution.

“In the past, in 2019, 2017, 2016 and 2012, visibility in Delhi dropped to 200 to 500 meters from October to November. These fog episodes are usually the result of high pollution, ”said RK Jenamani, scientist at IMD.

A study by scientists from the Indian Institute of Tropical Meteorology and the India Meteorological Department published in the Journal of Aerosol and Air Quality Research (AAQR) in 2017 said the frequency and intensity of fog episodes in Delhi during the winter season over the year has increased in the last decade (2006 to 2016) due to the high level of pollution.

“The role of atmospheric aerosols is very important in the life cycle of fog in urban areas,” the study says.

The study also showed that the thick fog in this part of the country is increasing. In the last winter season, between December 2020 and February 2021, there were 24 foggy days in Delhi compared to 16 foggy days in winter 2019-20.

“There is ample literature showing that fog periods are increasing and this forecasting system will help agencies avoid flight delays and address the problem of flight cancellations. This system will also prove beneficial in avoiding road accidents due to poor visibility while driving, ”said Govardhan.