The onset of the main fog season in the new year raises the prospect of additional diverted flights to neighbouring airports. Already recent unseasonal dense fog has forced at least 15 Etihad flights to be diverted from Abu Dhabi Airport for temporary landings in Al Ain, Muscat and Doha since Christmas Eve. Six consecutive mornings last month approached record low visibility. Abu Dhabi Airports Company (ADAC), which manages the airport, had been expected to receive its full CAT 3B certification by October, when it opened its second runway. The certification would have allowed it to operate flights in conditions with 75 metres of visibility rather than 125 metres.
With visibility hovering above 125 metres on most foggy mornings this week, Etihad's long-haul flights using its wide-bodied fleet landed safely and on time. "It's important to realise that flights from Sharjah and Dubai were also diverted this week, and Abu Dhabi airport is working harder than most to receive the new certification," an official at ADAC said. Meteorologists say the strongest fog conditions typically occur in February, March and October, with two types of fog conditions. In winter, fog is caused most often by heat radiation, where the cooling land temperature during the hours of darkness causes moisture in the air to condense. In the summer, fog is most often formed by a process known as advection, when moist air sweeps in from the Gulf and condenses.