UAE forecasters issue fog alert for coming days

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  Early morning fog shrouds the Dubai Expo 2020 metro line near Discovery Gardens on Tuesday. Pawan Singh / The National

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  A deluge of mist and fog this week followed one of the coldest starts to January in years. Pawan Singh / The National

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  Drivers were urged to be cautious as poor conditions made the roads perilous. Pawan Singh / The National

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  An eerie image of Discovery Gardens near Jebel Ali early on Tuesday. Pawan Singh / The National

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  Tuesday's fog lingered for several hours, slowing traffic and leading to length tailbacks

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  A petrol station shrouded in early morning fog on Tuesday. Pawan Singh / The National

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  Dense fog greeted morning commuters and residents of Dubai And Abu Dhabi as they headed out to start the day. Antonie Robertson / The National

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  Visibility was down to a few dozen metres in many areas. Antonie Robertson / The National

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  Workers work along the side of the E10 highway in Abu Dhabi. Victor Besa / The National

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  The fog affected most parts of the country on Tuesday

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  Police reduced speed limits on many major roads as the bad weather impacted visibility

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  Fog is a visible aerosol of minuscule water droplets – like a cloud on, or just above, the ground

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  The blanket stretched all the way from the coast to deep inland, almost reaching the UAE’s borders in the south

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  Forecasters issued a red alert as visibility dropped to less than 1,000m, and police warned drivers not to exceed 80kph

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  First introduced in 2019, the variable speed limit system is activated during bouts of bad weather, such as heavy rain, fog or during sandstorms

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  Anyone driving faster than 80kph when variable speed limits are in force will be fined

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  The decision to reduce speed limits made using weather reports, sensors installed on smart gates that estimate the visibility range and reports from police patrols

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  The fog season begins in mid-December and runs until the end of March, aided by clear skies and calm conditions

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  Dense fog greeted morning commuters and residents of Dubai as they head out to start the day. Antonie Robertson / The National

The UAE is set to be blanketed by fog for the rest of the working week as humidity rises overnight.

The murky weather could affect some coastal and internal areas on Wednesday, Thursday and Friday morning, said the National Centre of Meteorology.

It will be accompanied by a rise in temperatures, climbing steadily from 24°C on Tuesday to a high of 30°C by Saturday in the capital.

It will be slightly cooler in Dubai, rising to around 29°C on Friday, before falling back to 28°C by Saturday.

The skies will be partly sunny.

The fog season typically begins in mid-December and lasts until the end of March.

Fog needs certain conditions to form, such as calm winds and a clear atmosphere. These are more common at this time of the year as the seasons change.

The water vapour in the air condenses around the dust or sand in the air, which explains why the UAE experiences so many foggy episodes.

The country has averaged 132 days of fog formation a year since records began in 2006, with the longest stretch recorded in 2010, when there were 17 days of fog and five days of mist in January.

About 95 per cent of the fog in the UAE is radiation fog, which forms in the early hours as heat absorbed by the Earth’s surface during the day radiates into the air, causing water droplets to form. It dissipates in the heat of the sun.

Advection fog, the other type, forms when warm, moist air passes over a cool surface, creating water vapour.

Both types of fog can result in extremely dangerous driving conditions.

Police in Abu Dhabi have regularly sent out alerts to motorists in recent weeks warning that speed limits would be cut to 80kph to guard against the hazardous road conditions caused by prolonged bouts of low visibility.

One person died and eight others were injured in a 19-vehicle pile-up in Abu Dhabi during thick fog last month.

In February 2018, a lorry ploughed into a line of traffic in heavy fog. In total, 44 vehicles were involved in the accident on the E311 road between Abu Dhabi and Dubai.

In 2011, one person died and dozens were injured in a crash involving 127 vehicles on the Abu Dhabi-Dubai motorway.