With dense fog haunting the Delhi airport even in February, this fog season is turning out to be one of the worst in more than two decades. In fact, it already is the third worst fog season since 1996.
“This whole season has seen long dense fog hours and it is the third worst fog season in the last 20 years. With two days of very dense fog already experienced in February, it might end up to be one of the worst,” said R.K. Jenamani, the Director-in-Charge of the Meteorological Department at the Indira Gandhi International Airport here.
Dense fog made a rather late entry this winter, with December not witnessing long dense fog hours. However, January more than made up for it with 429 hours of fog, including 24-hour long dense fog cover on some occasions. A total of 750 fog hours were witnessed in December 2015 and January 2016, the third-highest since 1996.
Despite the record number of fog hours, flight disruptions this winter were comparatively painless compared to the previous few winter seasons.
The most significant marker of this trend was the rather low number of flight diversions and cancellations this time. A high number of diversions take place due to sudden onset of fog, which takes airlines by surprise.
The weatherman had carried out a ‘fog campaign’ this winter, which saw about 31 new equipments being brought to Delhi from different centres, apart from many specialists who also camped at the airport to study fog characteristics.
“This season, our forecast about onset and lifting fog was more accurate than previous seasons. Our forecast was 85 per cent to 87 per cent accurate this time compared to the usual accuracy rate of 70 per cent to 75 per cent,” Dr. Jenamani said.
He added that the Department was able to provide the exact time of fog onset instead of a broad period, which helped airlines plan their flight schedules.
“We have better equipment this time and airlines also demonstrated that if they follow Meteorological Department data, it results in less disruptions. During the fog campaign, we were able to provide additional fog trends, including build-up of pollution in the atmosphere,” Dr. Jenamani added.
The new equipment, including a radiometer made in Germany that cost about Rs.1crore, was brought in. It helped gauge the distribution of cloud and water vapour up to 10 km up in the air. “It provided vertical transformation and relayed findings continuously. Earlier, we relied only on surface parameters. Looking at the findings, we could find out about vapour incursion and how it was transferring to droplets. This gave us more lead time for our forecasts,” he said.
Not all equipment was imported. The older Australian-made Runway Visual Range (RVR) assessment system at the airport was replaced by the indigenously built Drishti equipment.
“Maintenance of foreign-made equipment is also a problem and these equipment are also not built for our extreme weather. Drishti, however, is capable of sustaining even the severest fog. The older equipment was used as back-up this time,” Dr. Jenamani added.
