Name: ____________________________________________ Date: ______________ Period: _________
Earth Science Chapter 20 Study Guide
1. List the direction of spin and direction of winds/air flow:
a. Northern Hemisphere low pressure system: ______________________________________________
b. Northern Hemisphere high pressure system: ______________________________________________
c. Southern Hemisphere low pressure system: ______________________________________________
d. Southern Hemisphere high pressure system: ______________________________________________
2. Centers of low pressure are called __________________________; centers of high pressure are called
_____________________________________.
3. What type of weather is associated with the following:
a. high pressure system: _____________________________________________
b. low pressure system: ______________________________________________
4. An immense body of air with similar properties at a given altitude is called a(n) _______________________.
5. What are the two defining or main characteristics of an air mass? ___________________________________
6. What will happen to a cold, dry air mass if it moves over warm, tropical waters?
_____________________________________________________
7. Where does an air mass get its characteristic properties from? ____________________________________
8. Air masses that form over water are called _________________________________; air masses that form
over land are called ____________________________________________.
9. Describe the temperature and moisture content of the following air masses:
a. mT: ______________________________________________________
b. mP: ______________________________________________________
c. cT: _______________________________________________________
d. cP: _______________________________________________________
10. List the 3 places where mT air masses that affect North America form: _____________________________
_________________________________________________________________________________________
11. _________ air masses originate in Siberia and often are altered to _________ as they travel over the Pacific
Ocean.
12. List the two air masses that affect the weather of North America the most: __________________________
13. “Nor’easters” are caused by ____________ air masses over New England.
14. Which air mass brings most of the precipitation to the U.S.? ____________
15. The boundary between two air masses is called a ____________________.
16. How do you indicate a cold front on a map? ______________________________________ How do you
indicate a warm front on a map? ________________________________________
17. The surface position does not move in a ___________________________ front because the flow of air is
______________________________ to the line of the front on either side.
18. What type of front forms when an active cold front overtakes a warm front? _________________________
19. Describe the precipitation of a warm front: ____________________________________________________
__________________________________________________________________________________________
20. Describe the precipitation of a cold front: _____________________________________________________
21. What is the first sign of an approaching warm front? _____________________________________ What is
the first sign of an approaching cold front? ________________________________________________
22. What shape do middle-latitude cyclones take? ____________________________
23. Briefly trace the steps of the life cycle of a middle-latitude cyclone: ________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
24. Pressure in a middle-latitude cyclone _______________________ towards the center.
25. List the stages of thunderstorm development & briefly describe what happens: _______________________
__________________________________________________________________________________________
__________________________________________________________________________________________
26. Where do the greatest number of thunderstorms occur? __________________________________________
27. When do thunderstorms form? ______________________________________________________________
__________________________________________________________________________________________
28. A rotating column of air is called a ________________________.
29. When are tornadoes most frequent? ____________________________________
30. Hurricane intensity is classified using the ______________________________________ scale; tornado
intensity is classified using the _____________________________ scale.
31. Typhoon is another name for a ______________________________.
32. Why do hurricanes lose energy over land? ____________________________________________________
_________________________________________________________________________________________