Air Mass

Arctic: comes from the Arctic Ocean , very cold and dry.
Continental Polar: comes from Siberia , cold and dry.
Maritime Polar: comes from the North Atlantic , cold and wet.
Continental Tropical: from Africa , warm and dry.
Maritime Tropical: from the Azores , warm and humid.

An air mass is a large body of air that has similar temperature and moisture characteristics throughout.

Air masses form over large areas of the Earth's surface and can be classified based on their temperature and moisture characteristics.

There are four main types of air masses: tropical (mT), polar (mP), arctic (A) and arid (cT) . These air masses can have an influence on the weather of an area when they move over it, which is often accompanied by a Front.