An Air Mass is a large volume of air which travels from one area to another. The weather an air mass brings is determined by the region it has come from and the type of surface it has moved over.
The five main air masses
There are 5 main Air Masses which affect The British Isles. You will need to be able to identify them and their characteristics.
To describe and explain the weather that air masses bring , think about the following:
- Where has your air mass come from: is it the Arctic Circle, the North Pole or the Tropics?
- Has the air mass passed over sea or land?
The two pieces of information above will help you name the air mass and describe its characterists. The basic ideas are as follows:
You should memorise the information in the table below to make sure that you can correctly identify the weather characteristics of air masses from each source area.
|Name||Source Area||Weather Characteristics|
|Tropical Maritime (mT)||Atlantic Ocean||Warm and wet|
|Tropical Continental (cT)||Southern Europe and North Africa||Warm and dry|
|Polar maritime (mP)||North Atlantic||Cold and wet|
|Polar Continental (cP)||Northern Europe||Cold and dry|
|Arctic Martime (mA)||Arctic Ocean||Very Cold. Not always wet due to low humidity|
Now look again at the map below. Make sure that you can name the 5 air masses and describe their characteristics. The source area will help you explain why each air mass has that particular characteristic.
The temperature of an Air Mass is also determined by seasonal changes. Temperatures in Summer months are always higher than in Winter months.
The Air Mass known as The Arctic Maritime does not occur very often, but when it does it brings with it heavy snow.