The science behind Europe’s Siberian chill this week

Nice out. The A48 in the snow. Image: Getty.

The so-called “Beast from the East” arrived in the UK this week, bringing unusually cold weather – about 7°C colder than the historical average for this time of year. Wind chill is making temperatures feel particularly arctic.

So how did the Siberian gusts come to arrive on Europe’s doorstep?

The movement of air across the globe, and the weather it brings with it, is governed by three major influences: gravity, the sun, and something called the Coriolis effect. The influence of gravity is simple, constantly pulling air towards the Earth’s surface.

The rise and fall of the sun dictates whether the air stays there. During the day, radiation from the sun heats the Earth, warming air directly above the surface and causing it to rise, leaving behind a region of low pressure (a low density of air particles). As the air rises, it cools and spreads outwards.

This mass of air, now denser than the air below it, sinks back down under the force of gravity, and naturally flows back towards the lower pressure region of air, creating a cycle of air circulation. These circulating patterns of wind exist on an intercontinental scale, transporting heat all the way from the tropics to the poles.

However, thanks to the Coriolis effect – the deflection of objects moving in a straight path due to the Earth’s rotation – the winds do not travel directly north or south. To illustrate this effect, imagine a spinning top. Parts of the spinning top closer to the spindle rotate at slower speeds than parts further away, as they have less distance to travel to complete a full circle. Similarly, the equator has to travel much faster than the poles do as the Earth rotates. As air travels north from the equator, its extra momentum compared to the slower rotating land that it is moving over makes it curve across to the east, while air travelling to the south pole curves westward.

In the northern hemisphere, this interaction between the Coriolis effect and the circulation systems produces the northern polar jet stream: high altitude currents of air blowing eastwards at hundreds of miles per hour, moving weather systems around the globe. This causes the UK’s prevailing westerly and south-westerly winds, which usually draw weather systems in from the relatively warm Atlantic and shield us from colder air masses to the east.

The shape of the jet streams is not rigid – it follows a meandering path, much like a slithering snake. Occasionally, the jet stream path can become so twisted that it folds back upon itself, reversing the direction of the prevailing wind, and drawing in cold air from the east.


This is exactly what just happened. In the last couple of days, the bitterly cold front combined with water vapour in the air to carpet the country in a blanket of brilliant white.

As the warmth of the sun disappears each night, the cold can feel all the more biting. But in the absence of the sun’s heat, the smaller difference in temperature between air near the ground and higher up makes air circulate more slowly. This often creates calmer conditions that might just provide a brief respite from the extra chill of the wind. For this same reason, air passengers generally experience smoother flying conditions when flying at night.

If you live in the city however, your experience of the “beast” can vary wildly from place to place. Cities continue to produce heat at night, generating their own microclimates. This man-made heat keeps air moving, and warms city dwellers up more than those in rural areas. At the same time, the ordered formation of buildings in cities creates strong wind corridors that are certainly best avoided at times like these.

Wherever you are experiencing this freezing weather, you can at least be thankful that you are here on Earth. Wind circulation patterns on other planets produce far more extreme weather than we will ever experience. Visitors to Venus, for example, would experience some serious turbulence when approaching landing, as the 500°C difference between surface and cloud generates extreme air circulation.

The ConversationHowever, if you were lucky enough to touch down and survive the experience of the crushing pressure found on Venus’ surface, you would feel nothing more than a gentle breeze, thanks to the planet’s very slow rotation, weak Coriolis effect, and dense air. You might want to seek shelter though – at close to 460°C, suddenly a cold chill doesn’t seem so bad.

Gareth Dorrian, Post Doctoral Research Associate in Space Science, Nottingham Trent University and Ian Whittaker, Lecturer, Nottingham Trent University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

What other British cities can learn from the Tyne & Wear Metro

A Metro train at Monument. Image: Callum Cape/Wikipedia.

Ask any person on the street what they know about Newcastle, and they’ll list a few things. They’ll mention the accent; they’ll mention the football; they’ll mention brown ale and Sting and Greggs. They might even mention coal or shipbuilding, and then the conversation will inevitably turn political, and you’ll wish you hadn’t stopped to ask someone about Newcastle at all.

They won’t, however, mention the Tyne and Wear Metro, because they haven’t probably heard of it – which is a shame, because the Metro is one of the best things the north-east has to offer.

Two main issues plague suburban trains. One is frequency. Suburban rail networks often run on poor frequency; to take Birmingham for an example, most of its trains operate at 30-minute intervals.

The other is simplicity. Using Birmingham again, the entire system is built around New Street, leading to a very simple network. Actually, that’s not quite true: if you’re coming from Leamington Spa, Warwick, Stourbridge, Solihull or a host of other major minor (minor major?) towns, you don’t actually connect to New Street – no, you don’t even connect to the ENTIRE SYSTEM BUILT AROUND NEW STREET except at Smethwick Galton Bridge, miles away in the western suburbs, where the physical tracks don’t even connect – they pass over each other. Plus, what on earth is the blue line to Walsall doing?

An ageing map of the West Midlands rail network: click any of the images in this article to expand them. Image: Transport for the West Midlands/Centro.

But Newcastle has long been a hub of railway activity. Tragically, the north-east has fewer active railway lines than any other region of the UK. Less tragically, this is because Tyne and Wear has the Metro.


The Metro was formed in 1980 from a somewhat eccentric collection of railways, including freight-only lines, part of the old Tyneside Electrics route, underground tunnelling through the city centre, track-sharing on the National Rail route to Sunderland, and lines closed after the Beeching axe fell in the early 1960s.

From this random group of railway lines, the Metro has managed to produce a very simple network of two lines. Both take a somewhat circuitous route, the Yellow line especially, because it’s literally a circle for much of its route; but they get to most of the major population centres. And frequency is excellent – a basic 5 trains an hour, with 10 tph on the inner core, increasing at peak times (my local station sees 17 tph each way in the morning peak).

Fares are simple, too: there are only three zones, and they’re generally good value, whilst the Metro has been a national leader in pay-as-you-go technology (PAYG), with a tap-in, tap-out system. The Metro also shares many characteristics of European light rail systems – for example, it uses the metric system (although this will doubtless revert to miles and chains post-Brexit, whilst fares will be paid in shillings).

 

The Metro network. Image: Nexus.

Perhaps most importantly, the Metro has been the British pioneer for the Karlsruhe model, in which light rail trains share tracks with mainline services. This began in 2002 with the extension to Sunderland, and, with new bi-mode trains coming in the next ten years, the Metro could expand further around the northeast. The Sheffield Supertram also recently adopted this model with its expansion to Rotherham; other cities, like Manchester, are considering similar moves.

However, these cities aren’t considering what the Metro has done best – amalgamated local lines to allow people to get around a city easily. Most cities’ rail services are focused on those commuters who travel in from outside, instead of allowing travel within a city; there’s no coherent system of corridors allowing residents to travel within the limits of a city.

The Metro doesn’t only offer lessons to big cities. Oxford, for example, currently has dire public transport, focused on busy buses which share the same congested roads as private vehicles; the city currently has only two rail stations near the centre (red dots).

Image: Google.

But it doesn’t need to be this way. For a start, Oxford is a fairly lateral city, featuring lots of north-south movements, along broadly the same route the railway line follows. So, using some existing infrastructure and reinstating other parts, Oxford’s public transport could be drastically improved. With limited engineering work, new stations could be built on the current track (blue dots on the map below; with more extensive work, the Cowley branch could be reinstated, too (orange dots). Electrify this new six-station route and, hey presto, Oxford has a functioning metro system; the short length of the route also means that few trains would be necessary for a fequent service.

Image: Google.

Next up: Leeds. West Yorkshire is a densely populated area with a large number of railway lines. Perfect! I hear you cry. Imperfect! I cry in return. Waaaaaah! Cry the people of Leeds, who, after two cancelled rapid transit schemes, have had enough of imaginative public transport projects.

Here’s a map of West Yorkshire:

Image: Google.

Here’s a map of West Yorkshire’s railway network:

 ​

Image: West Yorkshire Metro.

The problem is that all of the lines go to major towns, places like Dewsbury, Halifax or Castleford, which need a mainline connection due to their size. Options for a metro service are limited.

But that’s not to say they’re non-existent. For example, the Leeds-Bradford Interchange line passes through densely populated areas; and anyway, Bradford Interchange is a terminus, so it’s poorly suited to service as a through station, as it’s currently being used.

Image: Google.

With several extra stops, this line could be converted to a higher frequency light rail operation. It would then enter an underground section just before Holbeck; trains from Halifax could now reach Leeds via the Dewsbury line. The underground section would pass underneath Leeds station, therefore freeing up capacity at the mainline station, potentially simplifying the track layout as well.

 

Image: Google.

Then you have the lines from Dewsbury and Wakefield, which nearly touch here:

Image: Google.

By building a chord, services from Morley northwards could run into Leeds via the Wakefield line, leaving the Dewsbury line north of Morley open for light rail operation, probably with an interchange at the aforementioned station.

Image: Google.

The Leeds-Micklefield section of the Leeds-York line could also be put into metro service, by building a chord west of Woodlesford over the River Aire and connecting at Neville Hill Depot (this would involve running services from York and Selby via Castleford instead):

The path of the proposed chord, in white. Image: Google.

With a section of underground track in Leeds city centre, and an underground line into the north-east of Leeds – an area completely unserved by rail transport at present – the overall map could look like this, with the pink and yellow dots representing different lines:

Et voila! Image: Google.

Leeds would then have a light-rail based public transport system, with potential for expansion using the Karlsruhe model. It wouldn’t even be too expensive, as it mainly uses existing infrastructure. (Okay, the northeastern tunnel would be pricey, but would deliver huge benefits for the area.)

Why aren’t more cities doing this? Local council leaders often talk about introducing “metro-style services” – but they avoid committing to real metro projects because they’re more expensive than piecemeal improvements to the local rail system, and they’re often more complex to deliver (with the lack of space in modern-day city centres, real metro systems need tunnels).

But metro systems can provide huge benefits to cities, with more stops, a joined-up network, and simpler fares. More cities should follow the example of the Tyne and Wear Metro.