Types of Air Mass

Air masses are categorised into four main types.

• Tropical continental (Tc)
• Tropical maritime (Tm)
• Polar continental (Pc)
• Polar maritime (Pm)

And two further sub-divisions.

• Arctic maritime (Am)
• Returning polar maritime (rPm)

Each of these air-mass types has its own distinctive combination of properties in terms of:

• temperature
• moisture content (relative humidity)
• change of lapse rate
• stability
• weather
• visibility