Air Masses & Fronts

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/visualizations/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_science/terc/content/visualizations/es2002/es2002page01.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