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
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 Winds
What 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
Cool Dry Air Sinks
Warm Moist Air Rises
Cool Dry Air Sinks
Cold Moist Air Rises
Cool Dry Air Sinks
Warm Moist Air Rises
Cool Dry Air Sinks
Cold Moist Air Rises
Very Cold Air Sinks
Cold Moist Air Rises
Cool Dry Air Sinks
Warm Moist Air Rises
Cool Dry Air Sinks
Cold Moist Air Rises
Very Cold Air Sinks
Very Cold Air Sinks
H
L
Cold Moist Air Rises
H
Cool Dry Air Sinks
L
Warm Moist Air Rises
Cool Dry Air Sinks
Cold Moist Air Rises
Very Cold Air Sinks
H
L
H
H
L
H
L
H
L
H
Wind Moves from HIGH
to LOW
Objects are
deflected to the
RIGHT in the
Northern
Hemisphere
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
Remember!
Wind gets its name
from the
direction it is blowing
FROM!
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
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 Winds
2. 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, 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?