Transcript Slides 2.3.1 to 2.3.8 - World Geography 3202

World Geography 3200
2.4 WINDS
 Understand the cause of winds
and how they affect climate
 Chapter 4
 Pages 59-67
2.3.1
Air moves from areas of high
pressure to areas of low pressure.
 Think of:
1. Air inside a balloon
2. Air exhaled from a person’s lungs
3. Air powered pellet gun
 The movement of air from high and low
pressures in the earth’s atmosphere are
responsible for wind!
 P. 59-61
2.3.1
What is Wind?
Wind: * It is the flow or movement of air.
* It results from air masses of different
temperatures lying next to each other
* The resulting pressure variation causes “wind” to
blow from high pressure area to low pressure area.
2.3.1 Define the term Prevailing
Wind. p.61-63
Prevailing Winds:
• They are regular,
predictable, normal
winds in the same
direction
• They are caused by
global convection
cells
More on these later!
2.3.2 Describe conditions that
result in Land and Sea Breezes
Sea Breezes:
1. During the day the land heats much faster than
the water, consequently the air over the land
heats and rises.
2. The rising air over the land leaves a relatively
low pressure. The air pressure over the water is
relatively high, therefore wind blows from high
pressure (water) to low pressure (land)
3. Hence the name 'sea breeze'—the wind is
blowing off the sea.
 Land Breezes:
1. The sea air is warmer than land air.
Because this air is warmer, it rises and leaves
a relatively low pressure over the sea.
2. The land air then blows to the low
pressure over the sea.
 Remember—winds are named for where
they come from.
 For example, easterly winds come out of the
east; southerly winds come out of the south;
sea breezes come from the sea.
2.3.2 Describe Conditions that result in
Land and Sea Breezes
Sea Breeze
•Land air is warmer than sea air
•Air rises over land, leaving a
relative low pressure
•Sea air moves to lower pressure
Land Breeze
•Sea air warmer than land air
•Air rises over sea, leaving a
relative low pressure
•Land air moves to lower pressure
2.3.6 Define windward, leeward
and rain shadow
 Windward is on the side facing the wind.
Wind carries precipitation
 Leeward is on the side sheltered away from
the wind. Wind is usually drier
 Rain shadow is a dry area on the leeward
side of a mountain
2.3.8 Explain the relationship between wind
systems and precipitation
 Prevailing winds blowing off the ocean and onto
the land results in high precipitation. Especially if
the wind is blowing off a warm ocean, like the
Indian Ocean or the south Pacific.
 If wind is blowing off the land, then there is very
little moisture in it, resulting in low precipitation.
 Knowing the direction of winds over
mountains is also important in predicting
precipitation.
 The windward side of a mountain is going
to receive the greatest rainfall, while the
leeward side will find itself in a rain
shadow.
2.3.8 Explain the relationship between
wind systems and precipitation
 How do the prevailing
1.
2.
3.
4.
5.

winds affect
precipitation in:
England
Midwestern U.S.
British Columbia
Northern Africa
Central Australia
Question #26 p. 67: