The bane of motorists returns as fog season rolls into the Emirates
A day of fog followed by a sandstorm may seem strange, but that’s how the UAE’s weather system works, writes Liz Cookman
The UAE may be well known as a winter getaway, but for those living in the country yearround the weather can prove a fickle friend.
From flash floods to dust devils, hazy orange skies to snow, the UAE displays a surprising variety of meteorological phenomena.
One that occurs more often than may be expected is fog. It shrouds skyscrapers in a fluffy white blanket and can make for some spectacular sunrise shots. But it can also wreak havoc on the roads and cause flight delays.
So how do you even have fog in the desert?
The UAE’s climate, according to the Koppen climate classification system, is BWh, which means it is a hot desert with low rainfall. No surprises there.
But what the UAE lacks in land-bound water it makes up for in seawater and 95 per cent of the country’s fog is radiation fog.
This fog most commonly forms in the UAE between mid-December and the end of March, aided by clear skies and calm conditions.
The cooling of the Arabian Sea by thermal radiation overnight causes air temperatures close to the surface of the water to fall.
This reduces the air’s ability to hold moisture, allowing condensation and resulting in low cloud or fog.
But this fog is not only limited to coastal areas. Sometimes, the same fog forms inland, caused by temperature radiation from the land during the late night and early morning. It can also take longer to lift.
The ideal conditions for radiation fog are calm or low winds, about 5kph, because strong winds interfere with the water condensation.
Also needed are a clear atmosphere, especially during the night and early morning – this leads to a rapid increase in temperature – and a high pressure system.
This is what the UAE is experiencing right now.
The UAE has “frequent fog”, the National Centre for Meteorology says. It averages 132 days of fog formation a year since records began in 2006, with the most January fog recorded in 2010, when there were 17 days of it and five days of mist.
But the fog can be held back by oil and salt particles.
It seems counter-intuitive that you can have a day of thick fog followed by a sandstorm, but that is how the Emirates’ weather system works.
And which one you end up with often depends on the direction of the wind.
If there is a solid flow of air coming from the south, perhaps from somewhere like the Empty Quarter, it can bring with it loose dust or sand.
Wind can also cause localised sandstorms.
Fog and dust make for treacherous driving conditions and there are accidents every year.
Experts advise motorists to switch on their fog lights, switch off hazard lights, drive at a reasonable speed and be careful when moving between lanes.