Winds

1. Winds

2. What is wind? The movement of air in a horizontal direction

3. What causes wind? The uneven heating of the Earth causes differences in air pressure.

4. Why does this happen? The Sun’s energy is more concentrated at the Equator and spread out more over the poles. Air over the equator is warm and less dense and has lower pressure. Air over the poles is cold and denser and has higher pressure.

5. Why does this happen? As warm air at the equator rises, cooler air from the poles will move in and replace it. Air pressure moves in a pattern from high to low.

6. Convection As warm air at the equator rises, cooler air from the poles will move in and replace it.

7. Global Convection Currents The density changes caused by temperature changes create convection cells. These cause circular patterns of air that circulate over the whole planet.

8. Global Wind Belts Where the convections cells meet, prevailing winds and jet streams form. They blow from one direction over a certain area of the Earth’s surface.

9. Jet Stream

10. Jet Stream • Forms high in the upper Troposphere between two air masses of different temperatures • Higher temperature difference = faster speed • Due to the Coriolis Effect, it flows around air masses. • Polar Jet: • It dips southward when frigid polar air masses move south. • It tends to stay north in the summer months.

11. Prevailing Winds • Named for the direction from which they blow: • Polar Easterlies – High latitudes blow east to west toward the equator • Westerlies – Mid latitudes blow west to east toward the poles • Easterlies (Trade Winds) – Low latitudes blow east to west toward the Equator

12. Prevailing Winds

13. The Coriolis Effect As the Earth rotates counterclockwise, the winds bend and curve around the Earth. Gustave-Gaspard Coriolis, an engineer and mathematician, described this effect as an inertial force in 1835.

14. The Coriolis Effect In the Northern Hemisphere, winds bend to the right of their direction of travel. In the Southern Hemisphere, winds bend to the left of their direction of travel. Let’s try a little investigation to see how this works.

15. The Coriolis Effect Weather patterns and systems move in a circular motion due to the bending of the winds caused by the Earth’s rotation.

16. Ocean Currents

17. Ocean Currents • Warmcurrents flow away from the equator. • Cold currents flow toward the equator.

18. Factors Influencing Currents Sun Wind Coriolis Gravity

19. Convection Cycle

20. Surface Currents Make up 10% of oceans’ water Up to maximum depth of 400 m Surface ocean currents are caused by the surface wind patterns.

21. Deep Water Currents Make up about 90% of oceans’ water Differences in density cause them to move. Differences in density are related to temperature and salinity. At high latitudes, they sink deep into the ocean basins. Temperatures are so cold, they cause the density to increase.

22. El Nino • Abnormally highsurface ocean temperatures off the coast of South America • Causes unusual weather patterns across the globe

23. El Nino Starts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South America This changes where the convection current occurs. Causing rain where it usually doesn't occur and drought where it usually rains

24. La Nina • Abnormally lowsurface ocean temperatures off the coast of SouthAmerica • Causes unusualweather patterns across the globe

25. Ocean’s Effect on Climate Ocean currents move more slowly than winds. Oceans hold more heat than the atmosphere and land. Cold currents will cause nearby coastlines to be cooler. Warm currents will cause nearby coastlines to be warmer. Where do the cold currents come from? The warm currents?

26. Predictable Patterns How do these currents affect the climate of the coastline?