Why does Manchester Airport have to close due to snow?

As areas of Greater Manchester woke up to a blanket of snow on Thursday morning, Manchester Airport said that it had to close its runways for the fourth day since Sunday.

At 9am on January 9, the airport announced that the runways were temporarily closed “due to significant levels of now” to allow the maintenance teams to clear them.

The runways reopened again an hour later, although the closure has had an impact on flight schedules, with some delayed by two hours or more, while other flights have been cancelled completely.

Runway closures have become an almost daily occurrence this week as temperatures plummet across the region, causing treacherous snowy and icy conditions.

The airport first closed its runways for three hours on Sunday, then again on Monday morning, and for a third time on Tuesday.

Even though flights can resume after the temporary closures, flight schedules can experience delays for the rest of the day. This occurs when an aircraft misses its take-off slot and has to wait for a gap in the schedule - which can take several hours.

This can be incredibly frustrating for passengers, potentially ruining their holiday plans. But why does Manchester Airport have to close its runways when there’s snow?

The airport uses sophisticated forecasting systems to help it prepare for snow. Due to its location in the ‘Cheshire Gap’, a stretch of low land that sits on the border between England and Wales, it’s more prone to snowfall.

Showers that develop in the Irish Sea move across into Cheshire, while winds from the north west also contribute. Add in cold temperatures and it's the perfect recipe for snow.

Ice is a particular issue for runways as the temperature of the ground at night is colder than the air, meaning any moisture on the ground can soon turn into ice, even if its warmer than 0C. Unlike on roads and pavements, grit can’t be used as it can damage aircraft.

At Manchester Airport, the runway is treated with de-icing fluid to prevent any moisture from freezing, while the surface is also slightly grooved to create more traction for aircraft.

But when the snow gets to a certain depth the airport has to close the airfield in order to fully mobilise its fleet of more than 30 snow-clearing vehicles, enabling them to clear the runways more quickly. Even a small amount of snow can have an impact; just one inch of settled snow means the teams have to clear more than 7,000 cubic metres of snow from the runways.

The vehicles which are deployed include nine Combined Jet Sweepers which are equipped with 12m snow ploughs to the front and high-powered snow blowers to the rear, each worth more than £100,000 each.

The airport also has nine tractor-mounted ploughs, six snow brushes and three de-icers, used to spread de-icing fluid on runways and taxiways. Five gritters are also used on roads and walkways, but not on parts of the airfield used by aircraft.

During the winter months the airport puts on extra staff to provide support, including an adverse weather standby team who can be deployed depending on the forecast.

You might be wondering why Manchester Airport has to close, while airports in much colder countries can operate as normal despite getting more snow. It’s partly down to the snow we’re more likely to get here in the UK.

Described as 'wet snow', it's much more challenging to clear than the 'dry snow' found in chillier countries.

When temperatures are closer to freezing point, snow is wetter, which means it's more likely to turn into slush and ice, making it more slippery and more difficult to clear. When temperatures are lower than -2C, snow is drier and easier to clear.

Kathryn Chalk, an operational meteorologist at the Met Office, explaining the difference between the two, said: "The size and composition of a snowflake depend on how many ice crystals group together and this will be determined by air temperatures. Snowflakes that fall through dry, cool air will be small, powdery snowflakes that don't stick together. This 'dry' snow is ideal for snow sports but is more likely to drift in windy weather.

"When the temperature is slightly warmer than 0 °C, the snowflakes will melt around the edges and stick together to become big, heavy flakes. This creates 'wet' snow which sticks together easily and is good for making snowmen."

While European airports like those in Germany and Switzerland can be prone to wet snow, airports in Nordic countries experience much colder temperatures, creating drier and finer snow.

Naturally, these locations experience a lot more of the white stuff than we do - for example Helsinki gets on average 97 snow days a year, far greater than the 13 days the UK could experience - and airports are significantly more equipped to deal with it.

Finavia, the firm which manages and develops 20 airports around Finland, including Helsinki, starts preparing for the winter season as early as the summer.

Helsinki Airport has a fleet of 200 vehicles for winter maintenance, including 21 sweeper blowers, 19 trucks for anti-skid operations and snow removal, 12 wheel loaders, 12 snow blowers, three friction tester vehicles and two motor graders. During the winter season sweeper blowers are used for up to 800 hours to clear the runways.

Maintenance teams have 13 minutes to clear runways of snow, although it's often achieved in 11 minutes. Closures of the runway are extremely rare.

As well as coping with Finland’s regular winter conditions, the airport also has a ‘targeted snow removal’ plan on days with abnormal snowfall. It involves cooperation between the maintenance team, air traffic control and ground handling companies, to clear aircraft parking spaces and ensure they can turn around on time.

While runway closures, flight delays and disruption are frustrating for passengers, the measures taken ensure the airport can operate as safely as possible during wintery weather, and help travellers get to their destination.

For more of today's top stories, click here.