Air Masses and Fonts Chapter 8 Section 3. Standards S 6.4.e Students know differences in pressure, heat, air movement, and humidity result in changes.

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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