1. Air Masses  Areas of air that have about the same density, temperature, humidity, and pressure.  Cold air masses usually move south towards the equator.  Warm air masses usually move north away from the equator.

2. Types of air masses  Maritime (m) – moist air from over the water  Continental (c) – dry air from over the land  Polar (P) – cool air masses from a sub polar region  Tropical (T) – warm air from near equator  Arctic (A) – VERY cold air coming from the Arctic  Combine the above to form air masses: –mP, cP, mT, cT, cA

4. Fronts  Fronts are where air masses meet  Weather most often occurs along “fronts”  Four different types of fronts: –Cold Fronts –Warm fronts –Occluded fronts –Stationary fronts

5. Cold Front

6. Warm Front

7. Occluded Front  When a cold front catches up to a warm front

8. Stationary Front

10. Clouds and precipitation at the fronts

11. Occluded Front clouds and precipitation

12. Low pressure and high pressure systems

13. (Backwards from previous slide)

14. “Cyclogenesis”

15. Typical Low Pressure System

17. More Animations  http://www.mesoscale.iastate.edu/agron206/animations/0 5_cnWfronts.html http://www.mesoscale.iastate.edu/agron206/animations/0 5_cnWfronts.html http://www.mesoscale.iastate.edu/agron206/animations/0 5_cnWfronts.html  http://www.classzone.com/books/earth_science/terc/conte nt/visualizations/es2002/es2002page01.cfm?chapter_no=vi sualization http://www.classzone.com/books/earth_science/terc/conte nt/visualizations/es2002/es2002page01.cfm?chapter_no=vi sualization http://www.classzone.com/books/earth_science/terc/conte nt/visualizations/es2002/es2002page01.cfm?chapter_no=vi sualization  Cyclogenesis http://www.physicalgeography.net/fundamentals/7s.html Cyclogenesis http://www.physicalgeography.net/fundamentals/7s.html Cyclogenesis http://www.physicalgeography.net/fundamentals/7s.html

18. Assignment  In groups of 2 (assigned by cards): Locate the Air masses on map with temperatures provided. After you do this, compare the data with a map that has weather stations on it. It should take no more then 15 minutes to do this.