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
(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.
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
There are 2 types of winds…
1. Local Winds
2. Global Winds
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
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.
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.
Prevailing Westerlies
• Strong winds
• Located in the belt from 30-60
degrees latitude in both hemispheres.
• Has an impact on the US weather
Polar Easterlies
• Cold, but weak winds
• Near the north and south poles
• US weather is influenced by these
• Cooling takes place between the 50-60
degree latitude as it approaches the poles
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
What brings certain weather phenomenon?
El Nino
La Nina
• occurs when the surface
 occurs when the surface
temperature rises above the
temperature falls below the
normal water temperature in
normal water temperature in
the Equatorial Pacific Ocean
the Equatorial Pacific Ocean
creating more humidity in the
creating a more dry atmosphere
atmosphere
 Known to create drought
• Known to increase number of
conditions
hurricanes
• Occur more frequently (every 37 years)
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?