Air Masses Fronts Air Mass Air Mass a

Air Masses & Fronts

Air Mass • Air Mass: a huge body of air that has similar temperature, humidity, and pressure – Can be spread out over millions of km 2 and up to 10 km deep

Types of Air Masses • Descriptors: – – – Tropical = warm Polar = cold Arctic = very cold Continental = dry Maritime = wet • Types of Air Masses: – – – Maritime Tropical: warm & wet Continental Tropical: warm & dry Maritime Polar: cold & wet Continental Polar: cold & dry Continental Arctic: very cold & dry

How Air Masses Move • Westerlies – major wind belt over the US, generally pushes air masses from west to east • Jet Streams: bands of high-speed winds about 10 km above Earth’s surface, also blow west to east • Front: the boundary between air masses – When air masses collide, they do not easily mix

Types of Fronts • Cold Front: fast moving cold air mass collides with slower moving warm air mass – Cold fronts tend to move quickly

Types of Fronts • Warm Front: faster moving warm air mass collides with slower moving cold air mass – Warm fronts tend to move slowly

Types of Fronts • Stationary Front: when two air masses collide and don’t move for many days

Types of Fronts • Occluded Front: a warm air mass is trapped between two colder air masses

Highs & Lows • Cyclone: a spiral of warm, rising air, creating an area of Low air pressure (L) – Spins counter-clockwise • Anticyclone: a spiral of cold, falling air, creating an area of High air pressure (H) – Spins clockwise