1. Air
Pressure
And
Wind
Chapter 19

2. Global
Winds

3. Air temperatures on Earth are imbalanced because of uneven heating by the sun.
The atmosphere acts as a giant heat-transfer system that balances out these differences.

4. Non-Rotating Earth Model (hypothetical model)
If Earth did not rotate and its surface was smooth and uniform  one pair of convection cells
Heated air at equator would rise to the tropopause and be deflected towards the poles
Cooled air at the poles would sink to the ground and be deflected back towards the equator

5. Rotating Earth Model (actual model)
Because the Earth rotates, is covered by both land and water, and has varying terrain  three pairs of convection cells

7. Local Winds .
Caused by either topographic effects or by variations in surface composition
(land and water)

8. Flow of cool air from water to land during the day
sea breeze
wind

9. Flow of cool air from land to water at night
land breeze
Flow of cool air from land to water at night
wind

11. Valley Breeze: Flow of warm air up the mountainside during the day
Mountain Breeze: Flow of cool air down the mountainside at night

12. How Wind is Measured

13. Wind Vane: instrument for measuring wind direction
Winds are named based by the direction from which they flow
Units are written as cardinal directions
(N, S, E, W) or as degrees in a circle (0o to 360 o)

14. Anemometer: instrument for measuring wind speed

15. El Niño
and
La Niña

16. Normal Conditions:
Location = Pacific ocean, near the equator, off of the coasts of Ecuador and Peru in South America
Strong trade winds push a strong, warm Equatorial Current towards the west ending near Australia

17. Causes upwelling of coast  cold, nutrient-rich water rises  supports huge food chain (anchovies)

18. El Niño (“the child” – occurs during Christmas every 3-7 years)
Warm countercurrents become unusually strong. This suppresses the upwelling and makes the cold, nutrient- rich coastal waters warm.
Causes abnormal weather patterns and changes in food production in South America

19. Global weather changes in some areas (localized phenomena) – rain in dry areas, drought in rainy areas, etc

20. La Niña
The opposite of El Niño occurs when the trade winds are stronger than normal and therefore the upwelling is increased and water is colder than normal

21. Causes different abnormal global weather changes – colder winters, more rain in wet areas, drier in dry areas, etc.
Can increase hurricane activity