Download W&C Ch.3 Sec.1

Air Masses and Fronts
OBJECTIVE: IDENTIFY THE MAJOR TYPES OF AIR MASSES
THAT EFFECT WEATHER IN NORTH AMERICA.
1. Air Mass: A huge body of air that has similar
temperature, humidity, and air pressure throughout.
2. Air masses are classified by temperature and humidity:
TROPICAL, POLAR, MARITIME, AND CONTINENTAL
3. 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
4. Maritime Polar Air Mass:
Forms over icy cold North Pacific and N. Atlantic Oceans
Brings Fog, rain and cool temperatures to the west coast.
5. 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.
6. 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.
9. There are 4 types of fronts – warm, cold, stationary, &
Occluded.
10. 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.
11. 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
12. 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.
13. 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.
14. Cyclone: A swirling center of low air pressure – from the
Greek meaning Wheel.
15. Cyclones and decreasing air pressure are associated with
Storms and precipitation.
16. Anticyclones: High Pressure centers of dry air.