Case Study - UK Weather system

I have looked into air masses, fronts, depressions and also weather forecasting and now its the time to look at how all of the above affects the weather conditions experienced in the UK

Characteristics of the UK climate

The overall climate in England is called temperate maritime. This means that it is mild with temperatures not much lower than 0ºC in winter and not much higher than 32ºC in summer. It also means that it is damp and is subject to frequent changes.

Britain has four distinct seasons of fairly equal length - spring, summer, autumn and winter. In winter it is colder and wetter and the days are shorter than in summer. Along with 4 seasons in the UK there are also regional variations in climate. Generally the South is warmer than the north, the West and North West experience higher levels of precipitation and are also generally windier than the rest of the UK

So what causes the variations in climate?

You can see the image below shows the winds that each part of the UK experience and the general conditions this brings to the UK.

Above is a map showing the predominant air masses. Each of these have typical weather conditions:

Arctic Air (A):

• Continental arctic (cA): Originating over the Arctic ocean in winter it brings extremely cold temperatures and very little moisture. 
• Maritime arctic (mA): From the same source region, but less dry and less cold - in a way less extreme.

Polar Air (P):

• Continental polar (cP): Originating from high latitudes this air mass often brings the cold, dry and clear weather in winter and also dry and warm weather in summer.
• Maritime polar (mP): Originating as continental polar air over the North America Cool, when heated by the relatively warm water bodies this air mass becomes rather unstable resulting in blustery showers over the sea and windward coasts.

Tropical Air (T):

• Continental tropical (cT): Originating from the arid and desert regions during summer. The least common air mass to affect the British weather however it can bring record heat to south-east Britain, particulary in late-summer.
• Maritime tropical (mT).Originating from the Azores this brings mild and damp conditions in winter and warm and muggy conditions during summer. This air mass approaches the British Isles from the west, leading to overcast skies with prolonged rain for the western half of the country.

So we can see that the general climate in the UK and the variations experienced are largely influenced by the various air masses ranging from Arctic Maritime through to Tropical Continental.

Additional to the air masses other factors influence the British weather:

Continentality- This is the tendency of land to experience more thermal variation than water, due to the land's lower specific heat capacity. Continentality affects both temperature and precipitation across the UK

Prevailing wind- Britain's prevailing winds come from a south westerly direction over the Atlantic. The winds are cool in the summer and mild in the winter.

Gulf stream- Ocean currents can have a dramatic effect on a countries climate. In the UK, the Gulf stream has a very large impact on the weather experienced due to our close proximity to the Atlantic ocean.

 

The Gulf Stream is a warm ocean current in the North Atlantic flowing from the Gulf of Mexico, northeast along the U.S coast, and from there to the British Isles. The Gulf of Mexico has higher air temperatures than Britain as it's closer to the equator. This means that the air coming from the Gulf of Mexico to Britain is also warm. It is believed to warm the UK by 5-8 degrees Celsius.  However, the air is also quite moist as it travels over the Atlantic ocean. This is one reason why Britain often receives wet weather.

Classroom task

The past three posts have all focussed on air masses, fronts and the direct effect of them on UK weather. A nice summary of this would be a weather forecast presentation. It would be a group task to encourage the students to work together. They would pick a part of the UK and make a weather forecast up. It would include weather symbols, fronts and explanations behind all weather including causes for the conditions. There are a lot of resources available on websites for examples of forecasts.