Global and Local Winds

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What causes wind?

Caused by a difference in air pressure due to

unequal heating of the atmosphere.

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?

Global WindsWhat roles do

composition, structure, and properties play in

our atmosphere?

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

Coriolis Effect

Global Winds

Global wind patterns are caused by: Coriolis Effect The land and sea makeup of Earth

Warm Moist Air Rises

Warm Moist Air Rises

Cool Dry Air Sinks

Cool Dry Air Sinks

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

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Wind Moves from HIGH to LOW

Objects are deflected to

the RIGHT in

the Northern

Hemisphere

• 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

Remember!

Wind gets its name from the

direction it is blowingFROM!

Visual of 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

There are 2 types of winds…

1. Local Winds2. Global Winds

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

What’s the difference?

How do sea and land breezes work?