Air masses
An A large body of air with similar characteristics of temperature and humidity. 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.
There are five main air masses which affect the UK as detailed by the map below.
The following questions help to describe and explain the weather that brings air masses together.
- Where has the air mass come from - is it the Arctic Circle, the North Pole or the Tropics?
- Has the air mass passed over sea or land?
These two pieces of information will help you name the air mass and describe its characteristics. The basic ideas are shown in the table below.
| Source area | Characteristics |
| Land | Dry |
| Oceans | Wet |
| Tropics | Warm |
| Arctic | Cold |
| Source area | Land |
|---|---|
| Characteristics | Dry |
| Source area | Oceans |
|---|---|
| Characteristics | Wet |
| Source area | Tropics |
|---|---|
| Characteristics | Warm |
| Source area | Arctic |
|---|---|
| Characteristics | Cold |
Weather characteristics
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 Maritime (mA) | Arctic Ocean | Very cold. Not always wet due to low humidity. |
| Name | Tropical Maritime (mT) |
|---|---|
| Source area | Atlantic Ocean |
| Weather characteristics | Warm and wet |
| Name | Tropical Continental (cT) |
|---|---|
| Source area | Southern Europe and North Africa |
| Weather characteristics | Warm and dry |
| Name | Polar Maritime (mP) |
|---|---|
| Source area | North Atlantic |
| Weather characteristics | Cold and wet |
| Name | Polar Continental (cP) |
|---|---|
| Source area | Northern Europe |
| Weather characteristics | Cold and dry |
| Name | Arctic Maritime (mA) |
|---|---|
| Source area | Arctic Ocean |
| Weather characteristics | Very cold. Not always wet due to low humidity. |
The temperature of an air mass is also determined by seasonal changes. Temperatures in the summer months are always higher than in winter months.
The air mass known as the A very cold and wet air mass. does not occur very often, but when it does it brings with it heavy snow.
Questions
Question
An air mass which moves over land from the Tropics is called _____ _____ and brings with it _____ _____ weather?
An air mass which moves over land from the A very hot, humid country or environment.. is called A warm and dry air mass. and brings with it warm, dry weather.
Question
An air mass which comes from the Tropic of Cancer, over the Atlantic Ocean, is called _____ _____ and brings with it _____ ______ weather?
An air mass which comes from the Tropic of Cancer, over the Atlantic Ocean, is called A warm air mass that has formed over the sea, within 30° of latitude from the equator. and brings with it warm, wet weather.