Air Masses and FontsChapter 8Section 3
StandardsS 6.4.e Students know
differences in pressure, heat, air movement, and humidity result in changes in weather.
Anticipatory
Language of the DisciplineAir masses
Tropical
Polar
Maritime
Continental
Front
Occluded
Cyclone
Anticyclone
Air Masses A huge body of air that has similar temperature,
humidity and air pressure at any given height
Types:
maritime tropical
Continental tropical
Maritime polar
Continental polar
Maritime PolarWarm, humid air masses form over
tropical oceans.
In summer they bring hot humid air.
Gulf of Mexico, and the Atlantic Ocean
Winter: can bring heavy rain or snow
Maritime PolarCool, humid air masses form over icy cold North
Pacific
Summer: brings fog, rain and cool temperatures to the West Coast
Continental TropicalHot dry masses form in dry Southwest and
northern Mexico
Hot dry weather to the southern Great Plains
Covers a smaller area than other air masses
Continental PolarCentral and Northern Canada, and Alaska
Air masses bring bitterly cold weather with very low humidity
Winter: Air masses bring clear, cold, dry air
Summer: milder
How Air Masses MoveIn the US, air masses are commonly moved by
the prevailing westerlies and jet streams.
Prevailing Westerlies: major wind belts and push aim asses from west to east.
Jet Streams: bands of high speed winds above Earth’s surface
Fronts: huge air masses collide with each other but do not mix. They have different temperatures and humidity collide. Storms and changeable weather develops.
Reviewcold air is dense and sinks. Warm air is less
dense and rises. When they run into each other the cold air slides under the lighter air. Warmer air is pushed up.
Types of FontsColliding air masses can form 4 types of fonts:
Cold fronts- move quickly and cause abrupt weather changes. After it passes, drier air moves in and brings clear skies, a shift in wind and lower temperature
Warm fronts- move slowly weather may be rainy or cloudy. After is passes through the weather is warm and humid
Stationary fonts- where warm and cool air meet, the water vapor in the warm air condenses into rain, snow, fog or clouds. It will stall over an area, it may bring clouds and precipitation
Occluded fronts- temperature near the ground become cooler. Warm air mass is cut off. As warm air cools, it condenses and weather becomes cloudy and rain or snow may fall.
CyclonesWheel
Swirling center of low air pressure
Cyclones and decreasing air pressure are associated with clouds, wind and precipitation
Warm air in the center rises and air pressure decreases
Cooler air blows towards a high pressure area
AnticyclonesHigh pressure centers of dry air
“highs” on a weather map. H
Descending air in an anticyclone generally causes dry, clear weather.
Winds spiral outward from the center and moves to areas of lower pressure.
Checking for Understanding
Where do continental polar air masses come from?
What type of weather do cold fronts bring?
What in an anticyclone?
Guided PracticeIndependent Practice
Worksheet
Stop! Have your answers checked
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