1. Air Masses Earth Science Mr. Margetan

2. Air Masses  Air Mass – A stationary or slow moving body of air with uniform temperature and humidity –Can be thousands of km in diameter –Take on characteristics of source region

3. Types of Air Masses  Classified according to source region –Polar (P): cold air masses from polar regions –Tropical (T): warm air masses from tropical regions –maritime (m): air masses formed over oceans –continental (c): air masses formed over land

4. Types of Air Masses  Four Main Types of Air Masses –(mP) maritime polar –(mT) maritime tropical –(cP) continental polar –(cT) continental tropical

5. Types of Air Masses  Examples: –An air mass from central Africa –An air mass from the Arctic Ocean –An air mass from the Caribbean Sea –An air mass from northern Canada

6. Critical Thinking #1  What type of air mass would likely form over the center of Africa? Describe the temperature and humidity of this air mass.

7. Air Masses of North America  Tropical Air Masses –(cT) Mexican –(mT) Pacific –(mT) Atlantic

8. Air Masses of North America  Polar Air Masses –(cP) Canadian –(mP) Pacific –(mP) Atlantic

9. Critical Thinking #2  What types of air masses would affect Northern Lebanon most often? Explain your reasoning.

10. Pressure Centers  High Pressure Center – Air descends and results in fair weather (middle of air masses)  Low Pressure Center – Air rises and results in potentially rainy weather (near fronts)

11. Critical Thinking #3  Based on what you have learned about moisture in the atmosphere, why would descending (sinking) air cause nicer weather and ascending (rising) air cause rainy weather?

12. Fronts  Fronts – Regions where two or more air masses collide –Fronts generally cause some amount of cloud cover and/or precipitation

13. Fronts  Warm Front – Warm moves into Cold = Light Rain  Cold Front – Cold moves into Warm = Heavy Rain and Storms  Stationary Front – Cold and Warm collide and neither moves = Long periods of rain  Occluded Front – Two colds push up a Warm = Heavy Winds and Storms

14. Critical Thinking #4  What type of front is most common at Northern Lebanon? Explain your reasoning.

15. Critical Thinking #5  What type of front is most dangerous? Explain your reasoning.