1. Global Winds
Earth Science
Fall 2017

2. As the World Turns…
Winds in the N. Hemisphere blow to the right, and winds in the S. Hemisphere blow to the left
This effect is caused by the rotation of Earth
Called the Coriolis Effect

3. Convection
Much of the solar energy that the Earth receives causes intense heating in the equatorial regions
This intense heat produces powerful convection in these areas
As the warm, moist air rises, it creates a zone of low pressure, clouds, and precipitation along the equator
As this warm air rises, it eventually reaches the troposphere and can rise no higher – it spreads outward toward the poles

4. Convection, cont’
As it spreads, it cools and sinks back down to the surface at about 30 degrees North and South of the Equator
This sinking air produces areas of higher pressure and drier conditions
Many of the world’s deserts are located in these high pressure areas, 30 degrees N and S of the equator

5. Convection, cont’
Some of this air, as it sinks, moves back toward the equator.
This air flowing back towards the equator produces what is known as the Trade Winds
Trade winds obtained their name from sailing ships used in foreign trade - these winds propelled the ships from Europe to the New World

6. Trade Winds - Summary Occur at 30 degrees north and south latitudes
Air sinks, warms, and moves toward the equator in a westerly direction (due to the Coriolis Effect)
At the equator, the air goes back to 30 degrees and starts back over again
This fits a model developed by George Hadley in 1735 (sometimes called Hadley Cells)

8. Doldrums Near the equator, where the trade winds meet Light winds
Air is rising, there are clouds and occasional showers – Low air Pressure
Hurricanes originate in this region
Also called Intertropical Convergence Zone (ITCZ)

9. Horse Latitudes
At 30 degrees north or south latitude, mostly over the ocean
Winds are light and weather is hot and dry
Air is sinking – High Pressure
Named by Spanish sailors who transported horses and had to throw them overboard
Calm winds prolonged their voyage and led to a water shortage

10. Westerlies Between 30-60 degrees North and South Latitude
Move toward the poles, curving east
Responsible for most of the movement of weather across the U.S. and Canada

11. Westerlies

12. Polar Easterlies 60 degrees N and S latitude
Formed when the air around the poles cool and spread outward
As it spreads out, they are pushed west due to the Coriolis Effect
Characterized by really cold air

13. Polar Easterlies

14. Global Winds

15. Jet Stream Narrow band of fast, high altitude, westerly winds
Divides the cold arctic air from the warmer air in the south
During the winter, it is closer to the equator