As the fog season begins, flyers at Delhi’s Indira Gandhi International (IGI) Airport may experience fewer delays and cancellations, with the airport’s meteorological department doubling the duration of its fog prediction window for better forward planning, according to officials aware of the development.

Until last month, airport officials could predict fog around 18 hours before its onset. Delhi airport officials said now they will be able to predict foggy conditions nearly 36 hours in advance, which will help airlines and Air Traffic Control (ATC) plan a better flight schedule, leading to fewer disruptions.

The advancement in prediction time is made possible because two institutes — the Indian Institute of Tropical Meteorology, Pune, and the National Centre for Medium-Range Weather Forecasting (NCMRWF), Noida — that relay meteorological data to the airport’s meteorological department have tripled the volume of data shared to airport officials, senior airport officials said.

This data includes real-time numerical model-based fog prediction guidance, for which the two institutes have collaborated with the United Kingdom Met office and weather forecast centres in the United States, senior scientist at NCMRWF, RK Jenamani, said.

“The additional detailed components like information concerning moisture, pollutants in the air, winds near the surface and in the lower boundary layer, are not only helping us improve the quality and accuracy of our predictions, but also help us predicting fog formation at the airport at least 36 hours in advance. The practice was started in November. Until then our advance predictions were limited to 18 hours,” Jenamani said.

In winters, airlines want to know in advance whether the conditions are CAT-III or CAT-II (categories of operations required for an aircraft to land in low visibility, particularly due to fog) when they are scheduled to land, he said.

Delhi airport’s three runways are certified for advanced CAT-III operations, which allow landing of the compliant aircrafts when visibility is as low as 50 meters, but only aircraft equipped with CAT-III visual equipment and trained CAT-III pilots can utilise the runway when visibility is low.

If airport officials are able to give predictions on conditions in advance, airlines will be able to schedule flights more efficiently.

An ATC officer, who asked not to be identified, said the improved fog prediction will help airlines plan their schedule in accordance. Since pilots need special training to operate CAT-III compliant aircraft, airlines will get more time to move schedules of their crew if needed, the official said.

“If they do not have a CAT-III compatible pilot onboard a flight and Met department predicts fog, the airline will get more time now to make last-minute changes to the crew. We believe this will streamline flight operations at Delhi airport,” the officer added.

With a footfall of around 69.23 million passengers per year, IGI Airport is the busiest airport in the country. The Delhi ATC operates and controls at least one flight every minute. Last month, the Delhi ATC set a new record by handling 1,438 flight operations in a single day breaking its own record of 1,398 earlier this year.

On January 18 this year, heavy fog hit at least 600 flights forcing flight operations to be suspended during peak hours, leading to a cascading impact on schedules, which lasted at least 7-8 hours. Similarly, on January 4, at least 400 flights were affected by the heavy fog, with delays running till late into the evening.

Dhanajay Kumar, spokesperson Air India, said that they expect the new system will improve their on-time performance and reduce the turnaround time during fog. “We are sure other airlines will also benefit from this,” he said.

Scientists said that advanced weather feed will also help them utilise the already available equipment to analyse real-time information. Currently, IGI officials use a microwave radiometer that gives detailed data on the temperature and moisture in the lower level of atmosphere which is very crucial for fog prediction.

“Often an aircraft that is diverted from Delhi to a neighbouring airport due to fog fails to land even there as the fog situation is no different at the latter airport… This year IMD also started advanced fog forecast information for 12 other airports which are equally vulnerable to fog, like Delhi. With this we can also help ATC decide where an incoming aircraft can be diverted to,” Jenamani said.

Global aviation safety expert Mark D Martin said that an early warning and pre-emptive foresight in weather prediction is a welcome; but it doesn’t help more than allowing airlines to reschedule their flights for an earlier departure.

“If visibility drops below airport minima, a flight will get diverted, even if you have the best CAT-IIIB aircraft and qualified pilot on-board. Passengers travelling on affected fogs day will continue to be affected, and the Delhi Airport as well as airlines should make amendments to ensure passengers and travellers aren’t affected,” Martin said.

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