Download Air Masses and Fonts

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 in
weather.
Anticipatory
Language of the Discipline
 Air masses
 Front
 Tropical
 Occluded
 Polar
 Cyclone
 Maritime
 Anticyclone
 Continental
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 Polar
 Warm, 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 Polar
 Cool, humid air masses form over icy cold North Pacific
 Summer: brings fog, rain and cool temperatures to the
West Coast
Continental Tropical
 Hot 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 Polar
 Central 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 Move
 In 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.
Review
 cold 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 Fonts
 Colliding 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.
Cyclones
 Wheel
 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
Anticyclones
 High 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 Practice
Independent Practice
 Worksheet
 Stop! Have your answers checked
 Workbook pages