1. Warm Up: How do fluids of different densities behave?
Recall that a fluid can be either a liquid or a gas
Materials: cardboard divider, plastic box, red food coloring, warm water, table salt, blue food coloring, cold water
Predict what you think will happen when the divider is removed.
Share your prediction
Observe and Record the demonstration

2. Which weather factors produce changes in weather?
Big Idea
Which weather factors produce changes in weather?

3. Air Masses and Fronts
Chapter 8, Section 3

4. Learning Goals
S.6.4.e Students know differences in pressure, heat, air movement, and humidity result in changes in weather.

5. Key Questions
What kinds of questions can you ask by looking at this picture?

6. Key Questions
What kinds of questions can you ask based on this picture?

7. Key Questions
What kinds of questions can you ask based on the picture?

8. Key Questions
SWBAT describe the major types of air masses in North America, and how they move.
SWBAT list the main types of fronts.
SWBAT explain what type of weather is associated with cyclones and anticyclones.

9. Air mass
A huge body of air that has a similar temperature, humidity, and air pressure

10. tropical
Warm air masses formed in the tropics have low air pressure

11. polar
Cold air masses with high air pressure

12. maritime
Air masses that form over oceans. (Like the word ‘marina’)

13. continental
Air masses that form over land

14. front
The boundary where air masses meet

15. occluded
Warm air mass is cut off from the ground

16. cyclone
A swirling center of low air pressure

17. anticyclone High-pressure centers of dry air
Cyclone – air moving upward
Anticyclone – air moving downward

18. Types of Air Masses
Four major types of air masses influence the weather in North America:

19. Types of Air Masses
Maritime Polar – cool humid air

20. Types of Air Masses Continental Polar – cold air
Maritime Polar – cool humid air
Continental Polar – cold air

21. Types of Air Masses Continental Polar – cold air
Maritime Polar – cool humid air
Continental Polar – cold air
Maritime Polar – cool humid air, pushed back out to sea

22. Types of Air Masses Continental Polar – cold air
Maritime Polar – cool humid air
Continental Polar – cold air
Maritime Polar – cool humid air, pushed back out to sea
Maritime Tropical– warm, humid air

23. Types of Air Masses Continental Polar – cold air
Maritime Polar – cool humid air
Continental Polar – cold air
Maritime Polar – cool humid air, pushed back out to sea
Maritime Tropical– warm, humid air
Continental Tropical – hot, dry air

24. Types of Air Masses Continental Polar – cold air
Maritime Polar – cool humid air
Continental Polar – cold air
Maritime Polar – cool humid air, pushed back out to sea
Maritime Tropical– warm, humid air
Maritime Tropical – warm, humid air
Continental Tropical – hot, dry air

25. How Air Moves
In the continental United States, air masses are commonly moved by the prevailing westerlies and jet streams.

26. How Air Moves
Cold front – fast moving cold air mass overtakes a warm air mass
Clouds will form
If there is a lot of moisture, rain or snow will occur
Sometimes, thunderstorms will happen if there is even more moisture
Afterward, clear skies.

27. How Air Moves
Cold front – fast moving cold air mass overtakes a warm air mass

28. How Air Moves
Warm front – warm air mass overtakes a slow moving cold air mass
If the air is humid, clouds and precipitation for several days.
If the air is dry, there will be scattered clouds for several days.
Afterward, it will be warm and humid.

29. How Air Moves
Warm front – warm air mass overtakes a slow moving cold air mass

30. How Air Moves
Stationary front – cold and warm air masses meet, but neither can move the other
Warm air condenses into rain, snow, fog, or clouds.
If the air mass doesn’t move, may lead to multiple days of heavy precipitation

31. How Air Moves
Stationary front – cold and warm air masses meet, but neither can move the other

32. How Air Moves
Occluded front – cold and warm air masses meet, but neither can move the other
Warm air is pushed up to the top
Cool air on the bottom will mix; temperature on the bottom will decrease.
Warm air on top will condense, can lead to clouds or even rainfall.

33. How Air Moves
Occluded front – cold and warm air masses meet, but neither can move the other

34. Cyclones and Anticyclones
Cyclones and decreasing air pressure are associated with clouds, wind, and precipitation.

35. Cyclones and Anticyclones
The descending air in an anticyclone generally causes dry, clear weather.

36. Key Questions
What are the major types of air masses in North America, and how do they move?

37. Key Questions
What are the major types of air masses in North America, and how do they move?
Maritime tropical, continental tropical, maritime polar, and continental polar

38. Key Questions
What are the major types of air masses in North America, and how do they move?
Maritime tropical, continental tropical, maritime polar, and continental polar
What are the main types of fronts?

39. Key Questions
What are the major types of air masses in North America, and how do they move?
Maritime tropical, continental tropical, maritime polar, and continental polar
What are the main types of fronts?
Cold fronts, warm fronts, stationary fronts, and occluded fronts

40. Key Questions
What are the major types of air masses in North America, and how do they move?
Maritime tropical, continental tropical, maritime polar, and continental polar
What are the main types of fronts?
Cold fronts, warm fronts, stationary fronts, and occluded fronts
What type of weather is associated with cyclones and anticylcones?

41. Key Questions
What are the major types of air masses in North America, and how do they move?
Maritime tropical, continental tropical, maritime polar, and continental polar
What are the main types of fronts?
Cold fronts, warm fronts, stationary fronts, and occluded fronts
What type of weather is associated with cyclones and anticylcones?
Cyclones and decreasing air pressure – clouds, wind, and precipitation
Anticyclones – dry, clear weather

42. Homework
Workbook Chapter 8 Section 3