Why does the UAE experience so much low-lying fog?

The Emirates is otherwise known for general lack of cloud cover

Reem Island in Abu Dhabi is covered in 2018. Emmanuel Samoglou / The National

Miguel Angel Jimenez and other golfers on the fog covered range at the Dubai Desert Classic in 2011. Mike Young / The National

Dense fog engulfs Abu Dhabi's Al Maryah Island in December 2017. Ravindranath K / The National

Towers in Dubai Media City during the early morning fog in Dubai in April 2020. Pawan Singh / The National

The Fairmont Marina peeks through the fog on the Corniche, Abu Dhabi, on a sunny morning. Victor Besa / The National

Morning fog descends over Dubai Marina in 2013. Sarah Dea / The National

The ground below is swallowed up by fog in Dubai. Antonie Robertson / The National

Only the tallest buildings in Dubai sometimes escape the blanket. Chris Whiteoak / The National

Window cleaners work on Al Ain Tower with view of Etihad Towers in the background in Al Khalidiyah, Abu Dhabi. Erica ElKhershi / The National

A variety of light captured during fog in Abu Dhabi. Ravindranath K / The National

A fisherman on a misty morning in 2016. Rich-Joseph Facun / The National

Morning fog burns off near Electra Street in Abu Dhabi on December 31, 2008. Rich-Joseph Facun / The National

Fog in Abu Dhabi seen from The Gate Towers on Reem Island in 2015. Irene García León for The National

A light fog covers the Dubai skyline in 2015. Sarah Dea / The National

Cars drive through the morning fog on 24th street in Abu Dhabi in 2009. Galen Clarke / The National

Gate Towers on Abu Dhabi's Reem Island in 2013. Silvia Razgova / The National

Fog over Dubai Marina in 2013. Sarah Dea / The National

Sheikh Zayed bridge engulfed in fog in 2017. Ravindranath K / The National.

Abu Dhabi city on Christmas morning, 2017. Khushnum Bhandari / The National

Fog in the city of Abu Dhabi on Christmas morning, 2017. Khushnum Bhandari / The National

The UAE flag stands in the clear against a misty backdrop in Abu Dhabi. Victor Besa / The National

A lady takes her morning walk amid the fog at the Khalifa City A in 2018. Victor Besa / The National

Fog engulfed with high humidity in Abu Dhabi. Rajesh Korde / The National

The Sheikh Zayed Bridge in Abu Dhabi. Victor Besa / The National

A man goes for an early morning cycle as fog covers Dubai on September 21, 2020. Chris Whiteoak / The National

Misty conditions around JBR in Dubai. Sarah Dea / The National

A worker walks through Khalifa City in Abu Dhabi. Victor Besa / The National

Fog over Dubai Marina. Courtesy Ollie Maher

Towers in JLT in Dubai in April 2020. Pawan Singh / The National

Cars emerge from early morning fog on Muroor Road in Abu Dhabi. Victor Besa / The National

Dense fog blankets the Abu Dhabi skyline with Etihad Towers visible. Erica ElKhershi / The National

Workers during early morning fog in the Discovery Gardens area in Dubai. Pawan Singh / The National

Dense fog engulfs Abu Dhabi's Al Maryah Island in December 2017. Ravindranath K / The National

Early morning fog in the Discovery Gardens area in Dubai. Pawan Singh / The National

The sun tries to break through a foggy sky in Dubai. Rajesh Korde / The National

The Corniche in Abu Dhabi in February 2018. Victor Besa / The National

The Dubai high rises peek out above the fog. Sarah Dea / The National

Fog hovers in Ras Al Khaimah. Jeffrey E Biteng / The National

A gloomy start to a day in Abu Dhabi in 2013. Delores Johnson / The National

A morning fog rolls in over Abu Dhabi at the public beach in Al Bateen on October 28, 2009. Rich-Joseph Facun / The National

Buildings on Al Maryah Island, Abu Dhabi wrapped in fog in 2013. Brian Kerrigan / The National

Thick morning fog over Dubai Marina. Mark Asquith / The National

Early morning fog around the Dubai Marina area. Antonie Robertson / The National

Dubai Marina has almost vanished in the fog with just the walkway visible in 2014. Jaime Puebla / The National

Dubai Marina in a mix of sunshine and fog in 2014. Jaime Puebla / The National

Fog reported in areas of Dubai, the Northern Emirates and Al Dhafra on Tuesday. Pawan Singh / The National

The seaside takes on a calm serenity in 2017. Ravindranath K / The National

Fog during the morning in the Tecom area in Dubai. Pawan Singh / The National

Reem Island's Gate Towers stand tall above the cloud line in Abu Dhabi. Thamer Al Subaihi / The National

Despite heavy fog in Abu Dhabi, a woman spends the morning along the shore in January 2011. Rich-Joseph Facun / The National

With its magnificent deserts, amazing architecture and beautiful waterfronts, the UAE offers photographers scenes that few other nations can match.

Perhaps the most striking of the many images of the Emirates are those that combine the country’s scenery with a natural phenomenon: early-morning fog.

In particular, photographs showing the skyscrapers of Sheikh Zayed Road in Dubai emerging above the fog into clear air are truly iconic and have attracted attention around the globe.

But what exactly creates this incredible sight, which tends to happen later in the year, as the weather cools?

What causes the low-level fog or clouds?

In the colder months, after a clear and calm night, the air is likely to be moist thanks to winds that blow in from the Gulf during the day.

The ground, however, will have lost much of the heat absorbed the previous day, a process called radiative cooling, which in turns cools the air above it.

In the early morning, the air temperature at ground level may be about 20°C, which may not be cold enough for fog to form (although on some occasions it will be cool enough and ground-level mist or fog will form).

Further up, perhaps at 500 or 1,000 feet, the temperature may be 16°C or 17°C, which is cool enough for the water vap

our in the air to condense into low cloud.

Go higher still, however, and the air may actually become warmer — something known as a temperature inversion — because it has not been subject to radiative cooling in the same way that air lower down has been. So the cloud or fog does not stretch far up, making the upper sections of the skyscrapers visible in the clear air.

While spectacular to witness, this effect is short-lived because, as the sun rises, it warms the air and the fog or cloud vanishes relatively quickly.

Why does much of the UAE get little cloud the rest of the time?

A major reason is the UAE’s latitude, with Abu Dhabi and Dubai sitting about 25 degrees north of the equator. Here, high pressure weather systems predominate.

To understand why, it is easiest first to consider conditions at the equator, which experiences the greatest amount of direct sunlight in the world. Here, the sun heats the air and causes it to rise.

“In the tropics, there are large regions where the air is rising,” says Prof Sandrine Bony, director of research at the French National Centre for Scientific Research (CNRS).

“The water vapour cools down when it’s ascending, causing it to condense and form clouds.”

This heavy cloud cover frequently results in rain, so equatorial regions are often some of the wettest on earth.

By contrast, at the subtropical latitudes, which lie between 23.5 and 40 degrees north and south of the equator, high pressure is more typical, in part because of wind patterns created by the rising air near the equator.

“As the air rises in the tropics, it starts being transported away from the tropics at higher latitudes,” says Prof David Schultz, professor of synoptic meteorology at the University of Manchester in the UK.

At subtropical latitudes, the air tends to descend, warming and meaning that, as Prof Schultz describes, it “is not favourable for the creation of deep, fluffy clouds”.

So heavy cloud cover in the UAE is rare.

“Many of the other deserts are in the subtropical latitudes, like Australia, the deserts of China, the deserts of North America. They’re devoid of lots of cloud because the air is descending,” says Prof Schultz.

How do local factors affect the UAE’s weather?

While global factors have a significant influence on the UAE’s climate, and are a key reason why cloud cover and rainfall in the Emirates is low, local elements also play a role.

As described in a 2019 scientific paper, "Total Cloud Cover Climatology Over the United Arab Emirates", published in the journal Atmospheric Science Letters, Fujairah has the UAE’s highest average total cloud cover (TCC), the proportion of the sky covered by clouds.

This is in part because of its proximity to the Hajar mountains, which cause air from the sea to rise, expand and cool, leading the water vapour to condense and form clouds and rain.

“The land-sea temperature difference, along with the presence of Al Hajar mountain chain along the eastern coast of the UAE, significantly influences TCC in Fujairah, leading to orographic [mountain-related] cloud formations,” wrote the authors, who were from Khalifa University and the National Centre of Meteorology, both in Abu Dhabi.

They said Fujairah’s vegetation also influenced upward air movements in a way that increased the emirate’s rainfall and cloudiness.

“Fujairah also lies on the coast of the Gulf of Oman, making it more susceptible to the effects of the Indian Monsoon through proximity to the Arabian Sea,” the authors added.

Al Ain had the next highest average TCC, while the lowest figures were recorded in Sharjah and Abu Dhabi.

Why does the UAE not have an annual monsoon?

Regional geography explains why India, for example, experiences a monsoon from June to September, but the UAE — which sits roughly in the middle of India in terms of latitude — does not.

In summer the Thar desert in north-west India heats up, forming a low pressure area that draws in moist air from the Indian Ocean, which lies south of the subcontinent. This moisture ultimately falls as the monsoon rains.

South of the Arabian peninsula, however, the African continent occupies much of the space, so there is no vast ocean providing moist air of the kind that sits south of India.

As a result, the same pattern, of moist air being drawn north onto land, does not produce the same results, although there are a few places on the Arabian peninsula, such as Salalah in Oman, that are famous for experiencing a monsoon season.

“There’s not going to be a lot of moisture from the south,” says Prof Schultz.

“There will be some, but not as dramatic as the air being flowed into India.”