To What Extent Is the Climate of the British Isles a Product of the Air Masses That Affect It?
The UK is located at mid-altitude (between 50 and 55oN) which means it doesn’t get very hot because the sun is never very high in the sky, but it also does not get very cold because there are a few hours of daylight, even in the winter. It is on the Northern edge of a Ferrel Cell which in turn means the surface winds bring warm air from the south and those rise, creating a low pressure system (depression). It is also surrounded by water and near the Gulf Stream making the UK warmer than many places at the same altitude.
Air masses are large volumes of air with similar temperature and water vapour content and which can cover vast areas and travel long distances. There are five main air masses that affect the UK. Each air mass brings different weather conditions which is why the UK’s weather is so variable. Firstly, there is the polar maritime air masses from the North Atlantic Ocean. They bring cold, wet air which causes cold weather and rain. Secondly, there is the Tropical Maritime air masses from the Atlantic Ocean. These bring warm, wet air, which causes warm weather and rain. Thirdly, there is the Tropical Continental air masses from Africa. They bring warm, dry air which causes hot, dry weather. Fourthly, there is the Polar Continental air masses from the Artic. They bring cold dry air which causes very cold, dry weather. These air masses can bring snow if the air picks up moisture from the North Sea. Lastly, there is the Artic Maritime air masses from the Arctic Ocean. They bring very cold, wet air which causes cold weather and rain.
Depressions from over the Atlantic Ocean, then move east over the UK. These usually form when the tropical maritime and polar air masses meet. This happens as follows, the warm air from the tropical areas, move north whereas the cold air moves south from the Polar Regions. These two air masses then encounter each other and when they do, the warm air mass as it is less dense, it rises above the cold air mass