1. Weather Air Masses May 19, 2008

2. Weather Weather is the state of the atmosphere at a given time and place. Meteorology is the study of processes that govern Earth’s atmosphere. The formation and interaction of air masses generate weather.

3. Origin of an Air Mass An air mass is a large body of air in the lower troposphere that has similar characteristics throughout. The temperature and humidity of an air mass depend on where the air mass originates. When an air mass travels from one area to another, it takes with it the temperature and humidity of its place of origin. As an air mass travels, its characteristics may change.

4. Types of Air Masses Meteorologists classify air masses according to where they originate. For North America, there are five classifications of air masses contingent on two variables. Movie of Air Masses

5. Continental or Maritime? The humidity or amount of moisture in an air mass depend on whether the air mass formed over land (continental) or sea (maritime).

6. Arctic, Polar, or Tropical? The temperature of each type of air mass depends on whether the air mass originates in an arctic, polar, or tropical region.

7. Continental Arctic Continental Arctic (cA) air masses originate in the arctic regions. –Very low temperature –Low humidity

8. Characteristics of Air Masses NameSymbolTemperatureHumidity Continental Arctic cAVery lowLow

9. Continental Polar Continental polar (cP) air masses originate over the inland regions of Alaska and Canada. –Low temperature –Low humidity May cause lake-effect snow!

10. Characteristics of Air Masses NameSymbolTemperatureHumidity Continental Arctic cAVery lowLow Continental Polar cPLow (Lake-effect)

11. Maritime Polar Maritime polar air masses originate over the ocean in high latitudes. –Low temperature (not as low as cP) –High humidity

12. Characteristics of Air Masses NameSymbolTemperatureHumidity Continental Arctic cAVery lowLow Continental Polar cPLow (Lake-effect) Maritime Polar mPLowHigh

13. Continental Tropical Continental tropical air masses form over deserts. –High temperature –Low humidity

14. Characteristics of Air Masses NameSymbolTemperatureHumidity Continental Arctic cAVery lowLow Continental Polar cPLow (Lake-effect) Maritime Polar mPLowHigh Continental Tropical cTVery highLow

15. Maritime Tropical Maritime tropical air masses originate over a warm tropical ocean. –High temperature –High humidity

16. Characteristics of Air Masses NameSymbolTemperatureHumidity Continental Arctic cAVery lowLow Continental Polar cPLow (Lake-effect) Maritime Polar mPLowHigh Continental Tropical cTVery highLow Maritime Tropical mTHigh

17. North American Air Masses

18. Closure Compare and contrast weather and climate. What is a meteorologist? What is an air mass? What determines the characteristics of an air mass? List the air masses that affect weather in the United States?

19. Homework Air Masses - Asssignment