1. Chapter 3 Section 1 Pages 76-82
Air Masses & Fronts
Chapter 3 Section 1
Pages 76-82

2. Air Mass A huge body of air with similar characteristics:
Humidity
Temperature
Air Pressure
Classified based on two questions…
Did the air mass form over water or land?
In what climate did it form?

3. Continental
Form over land, in the middle of continents
Very dry air.

4. Maritime Form over oceans
Water evaporates from the ocean creating very humid air.

5. Tropical
Warm air masses form in the tropics and have low air pressure. Why?
Particles are spread out, low density.

6. Polar
Cold air masses form north of 50°N latitude and south of 50°S latitude
Have high air pressure (are very dense).

7. Air Masses 1 2 4 3 Continental Polar Maritime Polar Maritime Polar
Maritime Tropical
Maritime Tropical 4 3
Continental Tropical

8. How Air Masses Move What moves an air mass from one place to another?
The Global Winds move air masses
The Prevailing Westerlies generally push air masses from west to east in the United States.

9. Exit Pass
What are the two ways air masses are classified? Give an example of a type of air mass.

10. Fronts The area where air masses meet and do not mix
Named after battle lines
Cause storms and a change in weather
Depends on the characteristics of the air masses and how they are moving.

11. Warm Fronts A warm air mass hits a cold air mass
Warm air rises over cold air – Why?
Warm air is less dense
Weather:
If humid air, light rain forms
If dry, scattered clouds form
After it passes, it is likely to be warm and humid

12. Warm Fronts

13. Cold Fronts Cold air bumps into warm air, pushing the warm air up
As it rises, it cools and forms clouds
Move faster than warm air mass, can cause abrupt weather changes
Weather:
Humid brings rain, T-storms, or snow
Dry air forms cloudy skies
After it passes, brings cool, dry air with clear skies and cooler temps.

14. Cold Fronts

15. Stationary Fronts
Occurs when cold and warm air masses meet, but neither can force the other to move
Water vapor in the warm air condenses into rain, snow, fog or clouds
If it stalls over an area, it can bring these conditions for several days.

16. Stationary Fronts

17. Occluded Fronts
Occurs when a warm air mass is caught between two cold air masses
Pushes warm air up over colder air, cutting the warm air off from the ground
Weather:
Cool ground temperature
Brings clouds, rain or snowy weather.

18. Occluded Fronts

19. What is a front? Briefly explain one type of front.
Exit Pass
What is a front? Briefly explain one type of front.

20. Surface Map

21. Surface Map

22. Surface Map

23. Cyclones Cyclone is Greek- meaning “wheel”
A swirling center of low pressure.
Spin counter-clockwise (due to coriolis effect winds are turned to the right in the NH)
L is short for Low Pressure
Air is moving towards the low
Air is rising, forming clouds and precip.
Bring LOUSY Weather

24. Anti-Cyclones Are areas of high pressure centers
Winds spiral out from the center towards areas of lower pressure.
Spin clockwise (due to coriolis effect winds are turned to the right in the NH)
H= short for High Pressure
Air is moving away from the high.
Cool air is sinking, and warms as it falls.
Clear, dry weather. (Brings HAPPY weather)

25. Mid-Latitude CyclonesH L

26. Mid-Latitude Cyclones