Air Masses and Fronts

What are air masses? Large Bodies of air Form when the air over a large region sits in one place for many days The air gradually takes on the characteristics of the land or water below it

How do air masses affect our weather? As an air mass moves, it brings its characteristics with it Changes weather Weather changes where air masses meet

What are the two characteristics that describe air masses? Two words each One for moisture One for temperature

When describing moisture what words can we use? The first word of an air mass tells one where the mass was formed (over water or land) Continental Air masses formed over land Air becomes dry as it loses moisture to the dry land below it DRY Maritime Air masses formed over water Air becomes wet as it gains water vapor from the water below it WET

When describing temperature what words can we use? The second word of an air mass tells whether an air mass was formed close to the equator or pole Tropical Air masses formed near the equator Air becomes warm as it gains energy from the warm land or water WARM AIR Polar Air masses formed closer to the poles Air becomes cool as it loses energy to the cold land or water COLD AIR

What are the 4 Major Air Masses? The four major air masses are: Maritime Tropical (moist warm air) Continental Tropical (dry warm air) Maritime Polar (moist cold air) Continental Polar (dry cold air)

What do you think can move air masses? Air masses can travel away from the regions where they form Can move with global winds Can move with jet streams As the air mass moves it changes

What is it called when 2 air masses meet? Fronts form between two air masses and clouds can form in this rising air

What are the four different types of fronts? Different fronts = different weather Four Front Types Cold Front Warm Front Occluded Front – We wont focus on this one Stationary Front

Describe cold fronts Move into regions quickly Mass of cold, dense air Warmer air ahead of it is pushed upward and condenses Produces tall cumulonimbus clouds with precipitation and heavy storms Followed by cooler and clearer skies

Describe warm fronts Slower than cold fronts. As the warm air moves in it gradually goes above the colder denser air. Moisture in the warm air condenses, producing cloud-covered skies. Cirrus clouds are a sign of a warm front approaching, followed by stratus clouds and then as it comes there will be many hours of rain or snow. After it passes the air is warmer

Describe stationary fronts Occur when air masses first meet or when a cold or warm front stops moving. The boundary between masses doesn’t move The air in each mass can still move sideways along the front or upward. Upward movement will produce cloudy skies. Whatever front advances first decides which it will be