Chapter 17 Section 2 Weather Patterns

1. Chapter 17 Section 2 Weather Patterns

2. 1. Why does weather constantly change? - because of movement of air and moisture in the atmosphere • a large body of air that has properties similar to the part of Earth’s atmosphere over which it develops • example: over land = dry • over tropics = warm 2. air mass

3. cool/ moist cold/ dry cool/ moist 3. What air masses affect the U.S.? warm/ moist warm/ moist hot/ dry

4. 4. How do winds blow? - from high pressure to low pressure 5. cyclones • winds in the northern hemisphere swirl in a counter-clockwise direction because of Earth’s rotation • associated with stormy weather

5. blow away from a center of high pressure • winds spiral clockwise • fair weather 6. anticyclones 7. barometer - Used to measure air pressure 8. Weather caused by pressure • Low pressure causes clouds • high pressure causes good weather

6. 1. front - a boundary between two air masses of different density, moisture, or temperature 2. weather at frontal boundaries - cloudiness, precipitation, and storms

7. 3. 4 types of fronts • cold - warm • occluded - stationary • cold air wedges under warm like a plow and forms clouds • big temperature differences cause thunderstorms or tornadoes • blue line with triangles 4. cold front warm air cold air

8. 5. warm front • lighter, warm air moves over cold air • wet weather • red line with semicircles warm air cold air 6. occluded front. • 3 air masses = cold, cool, and warm • cold moves toward cool and pushes warm air up • purple lines with triangles and semicircles warm air cold air cool air

9. 7. stationary front • a boundary between air masses that stops advancing • light wind and precipitation • alternating red and blue line cold air warm air