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This chapter discusses the major types of air masses that affect weather in North America, including tropical, polar, maritime, and continental air masses. It also explores the four types of fronts: warm, cold, stationary, and occluded. Learn how these air masses and fronts interact to influence weather patterns in the region.
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Air Masses and Fronts Chapter 3Section 1
OBJECTIVE: IDENTIFY THE MAJOR TYPES OF AIR MASSES THAT EFFECT WEATHER IN NORTH AMERICA.
Air Mass: A huge body of air that has similar temperature, humidity, and air pressure throughout. • Air masses are classified by temperature and humidity: • TROPICAL, POLAR, MARITIME, AND CONTINENTAL • Maritime Tropical Air Mass: • Forms over oceans near the tropics – Gulf of Mexico, Pacific • Brings Hot humid weather in summer, Heavy rain and snow in • winter • Maritime Polar Air Mass: • Forms over icy cold North Pacific and N. Atlantic Oceans • Brings Fog, rain and cool temperatures to the west coast. • Continental Tropical Air Mass: • Forms only in summer over dry areas of the Southwest and • Northern Mexico-Brings Hot, Dry weather to S. Great Plains.
Continental Polar Air Mass: • Form over central and Northern Canada and Alaska • Bring clear, cold, dry air to most of North America in winter and • Storms in summer. 7. How air masses move: From West to East. 8. Front: The area where the air masses meet and do not mix. • There are 4 types of fronts – warm, cold, stationary, & • Occluded. • Cold Front: Rapidly moving cold air mass runs into a slow • Moving warm air mass pushing the warm air mass up and causes • Rain and thunderstorms.
Warm Fronts: A rapidly moving warm air mass collides with • a slow moving cold air mass and it goes over the cold air mass. • Causes: showers , light rain, and fog in summer – Snow in winter • Brings: Warm, humid weather • Stationary Front: Cold and warm air masses meet but neither • Has enough force to move the other. • Causes: Rain, snow, cloudy weather & fog. • Brings: many days of the same. • Occluded Front: Most complex situation – A warm air mass is • Trapped between two cold air masses. They push the warm air • Above them and the two cool masses mix. • Cyclone: A swirling center of low air pressure – from the • Greek meaning Wheel.
Cyclones and decreasing air pressure are associated with • Storms and precipitation. 16. Anticyclones: High Pressure centers of dry air.