Air Masses and Fronts

1. Air Masses and Fronts

2. I. Types of Air Masses • air mass- huge body of air that has similar temp, humidity, and air pressure at any given height. • Scientists classify them according to their temperature and humidity. • Four Types- 1. Maritime tropical 2. Continental tropical 3. Maritime polar 4. Continental polar

3. Maritime- wet or humid • Continental- dry • Polar- cold (high pressure-many of air molecules) • Tropical- warm (low pressure- few air molecules)

4. A. Maritime Tropical 1. Warm, humid air masses that form over tropical oceans. 2. Mainly on west coast. 3. Summer- hot, humid weather 4. Winter- heavy rain or snow.

5. B. Maritime Polar • Cool, humid air mass formed over icy cold North Pacific and North Atlantic oceans. • Summer- cool, humid air. Fog, rain and cool temps occur.

6. C. Continental Tropical • Hot, dry air masses form mostly in summer over dry areas of SW and northern Mexico.

7. D. Continental Polar • Cold, dry air mass formed near Arctic Circle. • Bring bitter, cold weather with very low humidity. • Winter- brings clear, cold, dry air.

8. II. How Air Masses Move • In the USA, air masses are moved from west to east by the a. prevailing westerlies b. jet streams- they carry air masses along. 2. Fronts- boundary where air masses meet. Storms and changeable weather develop there.

9. III. Types of Fronts • Cold front- 1. fast moving cold air mass runs into slow moving warm air mass. 2. Denser, cold air slides under lighter warm air. 3. warm air is pushed up. 4. resulting weather- cloudy skies or precipitation.

10. Cold Front

12. B. Warm front • Fast moving warm air mass overtakes a slowly moving cold air mass. • Cold air is denser, so warm air moves over cold air. • Warm air fronts move slowly, so it may be rainy or cloudy for days. • Resulting weather- clouds and precipitation.

13. Warm Front

15. Teach your neighbor what happens in a cold front and a warm front. Include what kind of weather it creates.

16. Draw a picture of a cold front and a warm front. You have 1 min. for each pic.

17. C. Stationary Front • Cold and warm air masses meet, but neither can move. • They have a “standoff”. • Resulting weather- many days of clouds and precip.

18. Stationary Front

19. D. Occluded Fronts • Warm air mass is caught btwn two cooler air masses. • Denser cool air masses move under the less dense warm air mass and push warm air upward. • Two cooler air masses meet in the middle and may mix. • Temp near ground becomes cooler. • Warm air mass is cut off from ground. • Resulting weather- cloudy and rain or snow.

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21. Occluded Front

23. Teach your neighbor what happens in a stationary front and an occluded front. Include the weather they create.

24. Draw a picture of a stationary front and an occluded front. You have 1 min. for each pic.

25. IV. Cyclones and Anticyclones • Cyclone- swirling center of low air pressure. • “L” on a weather map means low pressure. • Winds spiral in toward the center of the system. • Moves counterclockwise in N. Hem. • Air rises in a cyclone, air cools forming clouds and precip. • Causes clouds, wind, and precip.

27. Anticyclones • Anticyclones- high pressure centers of dry air. • Usually called “highs- “H” on a weather map. • Winds spiral outward from the center, moving towards areas of low pressure. • Moves clockwise in N. Hem. • Causes dry, clear weather

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31. Air masses weatehr