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Solar Radiation
CHECK YOUR NEIGHBOR
Atmospheric pressure is greatest near the Earth’s surface
because
A.
B.
C.
D.
of the weight of all the air above.
90% of Earth’s atmosphere is in the troposphere.
of warmer temperatures.
of water vapor.
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Solar Radiation
CHECK YOUR ANSWER
Atmospheric pressure is greatest near the Earth’s surface
because
A.
B.
C.
D.
of the weight of all the air above.
90% of Earth’s atmosphere is in the troposphere.
of warmer temperatures.
of water vapor.
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Solar Radiation
CHECK YOUR NEIGHBOR
The “ozone hole” is considered to be a problem, because
ozone
A.
B.
C.
D.
is a pollutant that creates smog.
depleted from the stratosphere contributes to an increase of
harmful UV rays at Earth’s surface.
is detrimental to life on Earth.
at the troposphere contributes to skin cancer.
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Solar Radiation
CHECK YOUR ANSWER
The “ozone hole” is considered to be a problem, because
ozone
A.
B.
C.
D.
is a pollutant that creates smog.
depleted from the stratosphere contributes to an increase of
harmful UV rays at Earth’s surface.
is detrimental to life on Earth.
at the troposphere contributes to skin cancer.
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Climate Zones
The world is divided into different climate zones.
Temperatures are:
• Highest in the tropics, near the equator
• Lower nearer the poles
• Moderate and variable in the temperate zone
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Temperature Depends on Latitude
Why does the temperature depend on
latitude?
Latitude affects
temperature
because the Sun’s
rays strike different
latitudes at different
angles.
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Temperature Depends on Latitude
When the Sun’s rays strike a surface at right
angles, the rays strike the smallest possible
area. They are the most concentrated at this
angle and have maximum solar intensity.
Solar intensity –
solar radiation per
area.
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Temperature Depends on Latitude
Which climate zone would have the highest
solar intensity?
Tropical
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Temperature Depends on Latitude
Which climate zone would have the lowest
solar intensity?
Polar
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Temperature Depends on Latitude
Temperate climate zones have a moderate
solar intensity.
Tropical
Temperate
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Polar
Days and Years
Earth’s revolution (orbit) around the Sun
determines the length of a year (365 days).
• Earth’s rotation on its axis determines day
length—24 hours in each day.
• The number of daylight hours varies during
the year depending on latitude.
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Why Are There Seasons?
When the Sun’s rays are closest to perpendicular
at any spot on the Earth, that region’s season
is summer.
Six months later, as the
rays fall upon the same
region more obliquely,
the season is winter.
In between are the
seasons fall and spring.
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Why Are There Seasons?
Variation in solar intensity with latitude and the tilt
of the Earth’s axis helps to explain the different
seasons.
The combination of more direct rays and longer
days creates the warmth of summer.
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Why are There Seasons?
At the summer solstice (June 21st),locations
north of the Arctic Circle in the Northern
Hemisphere have ~24 hours of daylight.
At the winter solstice (December 22nd),
locations north of the Arctic Circle have ~24
hours of night.
In the Southern Hemisphere, the Antarctic
Circle, the seasons are reversed (summer
solstice is in December).
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
CHECK YOUR NEIGHBOR
On the fourth of July in Kansas City, Missouri, the season
is _________. On the fourth of July in Perth, Australia, the
season is ___________.
A.
B.
C.
D.
winter; spring
summer; fall
summer; winter
winter; summer
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
CHECK YOUR ANSWER
On the fourth of July in Kansas City, Missouri, the season
is _________. On the fourth of July in Perth, Australia, the
season is ___________.
A.
B.
C.
D.
winter; spring
summer; fall
summer; winter
winter; summer
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Flow of the Atmosphere - Wind
If you puncture a tire or a
balloon, you can hear and feel
the air escaping. Why does the
air rush out of the balloon and
tires?
• Air moves naturally from a
region of high pressure to a
region of low pressure.
Wind is air that flows horizontally from higher
pressure to lower pressure. Larger differences in air
pressure produce stronger, faster winds.
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Flow of the Atmosphere - Wind
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What Causes Differences in Air Pressure?
• Pressure differences are caused by uneven heating of the
Earth’s surface.
Warm air characteristics:
• Warm air expands
• Warm air has lower density
and lower pressure
Cool air characteristics:
• Cool air contracts
• Cool air has higher density
and higher pressure
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Local Winds
• Not all surfaces are heated equally.
Example: Land heats and cools
more rapidly than water.
• Unequal heating results in pressure
differences. And pressure
differences result in wind.
Remember: Wind is air that flows
horizontally from higher pressure to
lower pressure.
Which way to does the sea breeze blow and why?
Animation of Sea Breeze
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Global Winds
Global Winds:
• Planet-scale differences occur because of solar intensity
variations—equatorial regions have greater solar intensity than
polar regions.
— Differences contribute to global wind patterns—prevailing
winds.
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The Coriolis Effect
Earth’s rotation greatly affects the path of moving air.
• Coriolis effect: moving bodies (such as air) deflect to
the right in the Northern Hemisphere, to the left in the
Southern Hemisphere.
• Deflection of wind
varies according to
speed and latitude.
— Faster wind, greater
deflection
— Deflection greatest
at poles, decreases
to zero at equator
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
CHECK YOUR NEIGHBOR
The prevailing westerly winds are affected by the Coriolis
effect by the deflection of winds
A.
C.
to the right in the Northern Hemisphere and left in the Southern
Hemisphere.
to the left in the Northern Hemisphere and right in the Southern
Hemisphere.
laterally toward the poles.
D.
westward.
B.
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CHECK YOUR ANSWER
The prevailing westerly winds are affected by the Coriolis
effect by the deflection of winds
A.
C.
to the right in the Northern Hemisphere and left in the
Southern Hemisphere.
to the left in the Northern Hemisphere and right in the Southern
Hemisphere.
laterally toward the poles.
D.
westward.
B.
Explanation:
Winds are named for the direction from which they
blow. Westerlies blow from the west to the east.
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Circulation of the Atmosphere Summary
Factors that affect wind:
• The pressure gradient force: air moves from high
pressure to low pressure
• The Coriolis effect: apparent deflection of winds due
to Earth’s rotation
• Frictional force: air moving close to ground
encounters friction
— Surface friction reduces wind speed, which reduces the
effect of Coriolis.
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Oceanic Circulation: Currents
• Ocean currents are streams of water that move,
relative to the larger ocean.
• Surface currents are created by wind.
– Surface ocean currents correspond to the directions
of the prevailing winds.
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Oceanic Circulation: Currents
Factors that influence ocean currents:
• For short distances, wind is strongest factor
• For longer distances, Coriolis effect comes into play:
—Coriolis causes surface currents to turn and twist
into semicircular whirls called gyres.
—Northern Hemisphere gyres rotate clockwise.
—Southern Hemisphere gyres rotate
counterclockwise.
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Oceanic Circulation: Currents
• Surface currents redistribute Earth’s heat.
• The Gulf Stream current carries vast quantities of
warm tropical water into higher latitudes.
– Great Britain and Norway have warmer winter temperatures
(for their latitude) because of the Gulf Stream.
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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Water in the Atmosphere
•Water vapor is water in the gaseous phase.
•Water vapor in the atmosphere produces
humidity, clouds, and precipitation.
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Humidity
• Humidity is the mass of water vapor a given
volume of air contains.
• There is always some water vapor in the air.
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Humidity
• Air that contains as much water vapor as it
possibly can is saturated.
– Warm air holds more water vapor than cold air.
– As air cools, it holds less and less water vapor.
• Saturation can occur when air temperature
drops, causing water vapor to condense.
• Saturation and condensation are more likely
in cold air—slower-moving molecules.
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Humidity
• Dew point is the temperature at which
saturation occurs.
• Condensation occurs when the dew point is
reached.
– Water vapor condenses high in the atmosphere and
forms clouds.
– Water vapor condenses close to the ground surface
to form dew, frost, and/or fog.
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Clouds
• Cloud - visible aggregate of minute water
droplets or tiny ice crystals.
• How do clouds form?
– Clouds form as moist, warm air rises, then
cools to its dew point and water vapor
condenses.
• Solid particles must be present for the water
molecules to condense on.
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Precipitation
• Precipitation – water in the liquid or solid
phase that returns to Earth’s surface from the
atmosphere.
• Rain, snow, sleet, hail, and mist.
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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley