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Global and Local Winds. i. What causes wind?. Caused by a difference in air pressure due to unequal heating of the atmosphere. - PowerPoint PPT Presentation
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Winds are created by….• Heating the air, decreases pressure (warmair 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.
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.
http://www.youtube.com/watch?v=mcPs_OdQOYU
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?
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
Warm Moist Air Rises
Cool Dry Air Sinks
Cool Dry Air Sinks
Cold Moist Air Rises
Cold Moist Air Rises
Warm Moist Air Rises
Cool Dry Air Sinks
Cool Dry Air Sinks
Cold Moist Air Rises
Cold Moist Air Rises
Very Cold Air Sinks
Very Cold Air Sinks
Warm Moist Air Rises
Cool Dry Air Sinks
Cool Dry Air Sinks
Cold Moist Air Rises
Cold Moist Air Rises
Very Cold Air Sinks
Very Cold Air Sinks
H
L
H
H
H
L
L
• 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
Global Winds
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.
• 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.
Trade Winds
Prevailing Westerlies
• Strong winds• Located in the belt from 30-60 degrees latitude in both hemispheres.• Has an impact on the US weather
• Cold, but weak winds• Near the north and south poles• US weather is influenced by these• Cooling takes place between the 50-60degree latitude as it approaches the poles
Polar Easterlies
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
Latitude Nicknames
Horse Latitudes 30 latitude 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
Jet Streams Jet Streams form at
latitudes where wind systems come together
High speed westerly winds form high above the surface
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, movingstorms
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
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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