1. Air Masses & Fronts

2. Air Masses Objective: to identify the different types of air masses & where they originate from.

3. Air Mass Defined: A large body of air found in the lower troposphere that is similar throughout in: humidity (wetness/dryness) and temperature

4. Air Masses cA- continental arctic, very cold and dry (from northern Alaska/Canada) cP- continental polar, cold and dry (from southern Alaska/Canada) (if travels over H2O, can cause snow) mP- maritime polar, cold and wet (from north pacific/Atlantic ocean) mT- maritime tropical, warm and wet (from gulf of Mexico) cT- continental tropical, warm and dry (from Mexico and central America) (since dry=no clouds)

6. Answer: 1. Where do cold & hot air masses originate? 2. Where do moist & dry air masses originate?

7. Jet Streams A fast moving stream of air found in the upper atmosphere (like a “river of air”) Found at 30 degrees and 60 degrees north and south of the equator (between convection cells where hot and cold air meet)

8. Fronts Objective: To identify the different types of fronts and how they are caused

9. Review: Air Masses An air mass is a large body of air that has similar temperature and humidity If an air mass forms over land (continental) it has low humidity If an air mass forms over an ocean (maritime) it has high humidity Air masses are either hot or cold

10. What happens when air masses run into each other? FRONTS! Air masses don’t mix together The boundary where the air masses meet is called a front Fronts are common at mid-latitudes, where tropical and polar air masses commonly meet

11. What happens when air masses run into each other? Air masses have different temperatures and humidity levels When they collide, the more dense air mass goes under the less dense air mass

12. Fronts A front is a place where two different air masses meet

13. 4 types of fronts: Each bring different types of weather

14. Cold Front Occurs when a polar (cold) air mass runs into (& replaces) a tropical (warm) air mass The warm air is less dense and gets pushed above the cold air mass http://www.classzone.com/books/earth_science/terc/content/vi sualizations/es2002/es2002page01.cfm

15. Cold Front Temperatures drop, and there is usually precipitation Thunderstorms are usually a result of a cold front

16. Warm Front Warm front- when warm (less dense) air moves forward (advances) and replaces cold air: forms a wedge shape. http://www.classzone.com/books/earth_sci ence/terc/content/visualizations/es2002/es 2002page01.cfm

17. Warm Front Results in warmer temperatures, often higher humidity Usually precipitation for several days http://www.atmosphere.mpg.de/enid/1__Weather___Fronts/ __Worksheet_1_4ap.html

18. Stationary Front Occurs when neither the warm air or the cold air is advancing The less dense warm air will rise above the cold air

19. Stationary Front Clouds and precipitation occur If a stationary front stays for too long, flooding can occur

20. Occluded Front Occurs when a cold front catches up with a warm front Cold fronts move twice as fast as warm fronts

21. Occluded Front Causes cloudiness and precipitation