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Global and Local Winds i
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What causes wind? Caused by a difference in air pressure due to
unequal heating of the atmosphere.
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Winds are created by…. • Heating the air, decreases pressure (warm air rises creating a low pressure) • Cool air rushes into replace the warm air (cooler dense air, produces high pressure) • As air goes from high to low pressure, winds form.
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Coriolis Effect • Coriolis Effect – Rotation of the Earth causes moving air and water to change directions • Northern Hemisphere winds curve to the right • Southern Hemisphere winds curve to the left.
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Do Now – In Binders Describe how wind is created.
What is the relationship between density and pressure? What happens to air pressure as I hike up a mountain? What instrument measures air pressure?
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Global Winds What roles do composition, structure, and properties play in our atmosphere?
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Coriolis Effect Because the Earth rotates, and consists of a mixture of land and sea, the Coriolis Effect exists The Coriolis Effect causes air movement to: Move to the RIGHT in the Northern Hemisphere Move to the LEFT in the SOUTHERN Hemisphere
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Coriolis Effect
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Global Winds Global wind patterns are caused by: Coriolis Effect
The land and sea makeup of Earth
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30 60 90 Warm Moist Air Rises
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30 60 90 Warm Moist Air Rises Cool Dry Air Sinks
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90 30 60 Cold Moist Air Rises Cool Dry Air Sinks Warm Moist Air Rises
60 90 Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Cold Moist Air Rises
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90 30 60 Cold Moist Air Rises Cool Dry Air Sinks Warm Moist Air Rises
60 90 Warm Moist Air Rises Cool Dry Air Sinks Very Cold Air Sinks Cold Moist Air Rises Cold Moist Air Rises Very Cold Air Sinks
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L H 90 30 60 Cold Moist Air Rises Cool Dry Air Sinks
60 90 Warm Moist Air Rises Cool Dry Air Sinks Very Cold Air Sinks Cold Moist Air Rises Cold Moist Air Rises Very Cold Air Sinks
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Wind Moves from HIGH to LOW
30 60 90 Wind Moves from HIGH to LOW
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Objects are deflected to the RIGHT in the Northern Hemisphere
30 60 90
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Global Winds • Don’t travel North and South because of the Earth rotating on its axis. • 4 Types of Global Winds – Doldrums – Trade Winds – Prevailing Westerlies – Polar Easterlies
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Wind gets its name from the direction it is blowing FROM!
Remember! Wind gets its name from the direction it is blowing FROM!
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Visual of Global Winds
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These are located at the equator, surface winds are calm and weak.
Doldrums These are located at the equator, surface winds are calm and weak. Why are they called doldrums? Sailors found that there were no winds near the equator for a period of time. The ships were essentially stuck in one place, not being able to move forward. These calm periods were called doldrums. Today, to be “stuck in the doldrums” means that you’d like to be doing something, but you’re stuck waiting for something to happen so you can begin moving forward.
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Trade Winds Named from their ability to quickly propel trading ships across the ocean - found between about 30° latitude and the equator - steady and blow about 11 to 13 mph - In the Northern Hemisphere, the trade winds blow from the northeast and are known as the Northeast Trade Winds - In the Southern Hemisphere, the winds blow from the southeast and are called the Southeast Trade Winds.
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Prevailing Westerlies
• Strong winds • Located in the belt from degrees latitude in both hemispheres. • Has an impact on the US weather
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Polar Easterlies • Cold, but weak winds • Near the north and south poles • US weather is influenced by these • Cooling takes place between the degree latitude as it approaches the poles
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Northern Wind Patterns
Polar Easterlies 90 – 60 latitude from the east Prevailing Westerlies 60 – 30 latitude from the west Trade winds 30 – 0 latitude from the East
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Latitude Nicknames Horse Latitudes
Named because the boats stalled and the horses had to go! Doldrums / Intertropical Convergence Zone (ITCZ) Equator Trade winds converge from north and south Named because boats also got stranded here
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Jet Streams Jet Streams form at latitudes where wind systems come together High speed westerly winds form high above the surface
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There are 2 types of winds…
1. Local Winds 2. Global Winds
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Jet Stream • Discovered in 1940’s
• Can be found in the upper troposphere • Strong high speed and high pressure • Moves west to east across the US, moving storms
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What brings certain weather phenomenon?
El Nino La Nina occurs when the surface temperature rises above the normal water temperature in the Equatorial Pacific Ocean creating more humidity in the atmosphere Known to increase number of hurricanes Occur more frequently (every 3-7 years) occurs when the surface temperature falls below the normal water temperature in the Equatorial Pacific Ocean creating a more dry atmosphere Known to create drought conditions
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Local Winds • Cover short distances • Blow from any direction • 2 Types of Local Winds – Sea Breezes- from sea to land – Land Breezes – from land to sea
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What’s the difference?
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How do sea and land breezes work?
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