1. Air Masses

2.  Weather changes when new air masses move into the area.  An AIR MASS is a large volume of air in which temperature and humidity are nearly the same.

3. Formation  They form when air sits over a large area for many days.  The air takes on the characteristics of the land or water below.  They can cover thousands of square miles.

4. Movement  As air masses move they bring their characteristics along with it

5. Review  What is an air mass? How can weather change with the arrival of a new air mass?

6. Characteristics  The characteristics of an air mass depend upon where they come from.  Every air mass has two names. –One for moisture –One for temperature

7. Moisture  The first word to describe an air mass tells where it was formed (how much water it contains).  Maritime (wet) – form over water.  Continental (dry) – form over land

8. Temperature  The second word describes the temperature or where it began.  Tropical (warm)– form closer to the equator.  Polar (cold) – form closer to the poles.

9. Examples  Continental Tropical: dry and warm  Continental Polar: dry and cold  Maritime Tropical: wet and warm  Maritime Polar: wet and cold

10. Review  What does each word of the air mass’s name represent?

11. Explain the Air Masses

12. Air Masses

13. Real World Uses  Meteorologists use abbreviations for the words.  Continental is written as “c”  Maritime is written as “m”  Tropical is written as “T”  Polar is written as “P”

14. Practice  Assign a name to the following –A wet, cold air mass –A dry, warm air mass –A dry, cold air mass –A wet, warm air mass

15. How do air masses move?  Global winds move air masses.  Generally move west to east in the U.S.  As the air mass moves, so does its characteristics.