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The
Atmosphere
Chapter 15
Page 392 – 419
Page 394
Characteristics of the Atmosphere
 Atmosphere
= a mixture of gases that surrounds
the Earth.
•
It protects us from the sun’s harmful rays.
•
It is always changing.

Every breathe we take, every tree we plant,
and every motor vehicle we ride in affects
the composition of the atmosphere
Pages 394 – 395
Composition of the Atmosphere
≈ 78% of the gases in the atmosphere. It
is released by volcanic eruptions & when dead
plants & animals decay.
 Nitrogen
≈ 21% of the gases in the atmosphere. It
is produced mainly by plants.
 Oxygen
 The
remaining 1% of the atmosphere is made up
of argon, carbon dioxide, water vapor, & other
gases.
 Besides
gases in the atmosphere there are also
small amounts of solids & liquids.
Pages 395 – 396
Atmospheric Pressure & Temperature
 Air
pressure = the measure of the force with which
the air molecules push on a surface.
 Air pressure, temperature, & the kinds of gases
present change through out the atmosphere.
Pressure
 Altitude = the height of an object above the Earth’s
surface.
 As altitude increases, air pressure decreases.
Air Temperature
 Air temperature varies depending on the way solar
energy is absorbed as it moves downward through the
atmosphere.
Page 396
Layers of the Atmosphere
 Based
on temperature the Earth’s atmosphere is
divided into four layers:
•
Troposphere
•
Stratosphere
•
Mesosphere
•
Thermosphere
 Each
layer has unique characteristics
Page 397
Troposphere
= lowest densest part of the Earth’s
atmosphere in which most weather changes occur;
temperature generally decreases rapidly with altitude
& it extends from the Earth’s surface to the bottom of
the stratosphere.
Stratosphere
 Stratosphere = air is thin & contains little moisture;
temperature is cold (-60oC) but rises with altitude
 Ozone = O3 molecule; Almost all ozone in the
atmosphere is contained the ozone layer. This layer
absorbs solar energy in the form of ultraviolet
radiation which protects life on Earth.
 Troposphere
Pages 398 – 399

Mesosphere
Mesosphere = coldest layer; temperature drops as
altitude increases (as low as -93oC). Scientists
recently discovered wind storms in the mesosphere.
Thermosphere
 Thermosphere (ionosphere) = uppermost layer;
temperature increases with altitude (as high as
1,700oC); nitrogen & oxygen absorb harmful solar
radiation which causes them to become ionic in nature
& reflect light & radio waves (Northern lights).
 There is no definite boundary between the atmosphere
and space. In the upper thermosphere, the air becomes
thinner & thinner, eventually blending into space.
Pages 400 – 401
Heating of the Atmosphere
 The
Earth’s atmosphere is heated by transfer of
energy from the sun.
Energy in the Atmosphere
 The Earth receives energy from the sun in the form of
radiation. Primary types of radiation reaching the
Earth’s surface from the sun are known as visible
light. When radiation is absorbed, its energy is
changed into heat.
 The Earth’s surface is heated as it absorbs energy
from the sun. The Earth transfers energy to the lower
atmosphere, heating it, & causing convection.
Page 401
Moving the Energy Around
 Most
heat in the atmosphere moves by convection,
but it is only one of many processes responsible for
redistributing energy on the Earth.
 Once incoming solar radiation passes through the
atmosphere & is absorbed by the Earth’s surface the
energy is transferred to the atmosphere by:
• Evaporation of surface water & its condensation in
the atmosphere
• Emission of infrared waves, which are then
absorbed by atmospheric gases
• Conduction as cool air comes in contact with
warm surfaces.
Pages 402 – 403

The
Greenhouse
Effect
Greenhouse effect = process in which the gases in the
atmosphere trap thermal energy
Global Warming
 Global warming = rise in the average global
temperatures
Keeping the Earth Livable
 radiation balance – the amount of solar energy received
& the amount of thermal radiation returned to space.
 Some scientists argue that humans are responsible for
the increased temperatures on Earth today
 Others argue that it has gone through warm periods
before people ever walked the Earth.
Pages 404 – 405
Atmospheric Pressure & Winds
 Wind
= moving air
Why Air Moves
 Wind is created by differences in pressure. These
differences in air pressure are caused by the unequal
heating of the Earth.
• Colder, more dense air is heavier & sinks = high
pressure.
• Air moves from high pressure to low pressure
 The speed of the wind is determined by the pressure
difference between the area of high pressure & the
area of low pressure.
Page 405
 The
Pressure Belts
uneven heating of the Earth produces pressure
belts. These belts occur at about every 30o of
latitude.
Coriolis Effect
 The
movement of wind is affected by the rotation
of the Earth so winds don’t blow directly north or
south.
 Northern
Hemisphere they curve to the right
 Southern
Hemisphere they curve to the left
Page 406
Types of Winds
winds – generally move short distances &
can move in any direction.
 Local
winds –These travel longer distances than
local winds & travel in a specific direction
because they are part of a pattern of air circulation
that moves across the Earth.
 Global
 Lets
take a look at some global winds before we
look at local winds
Pages 406 – 407
 Trade
Trade Winds
winds = in both hemispheres, the winds
that blow from 30o latitude to the equator
•
Northern Hemisphere they blow from the
northeast to the southwest
•
Southern Hemisphere they blow from the
southeast to the northwest.
 Early
traders used these winds to sail from Europe
to the Americas.
Page 407
Westerlies
 Westerlies
= wind belts found in both the
Northern & Southern Hemispheres between 30o &
60o latitude. These winds flow toward the poles in
opposite directions form the trade winds.
•
Northern Hemisphere they blow from the
southwest to the northeast
•
Southern Hemisphere they blow from the
northwest to the southeast.
 These
winds helped sailors return to Europe.
Page 407
Polar Easterlies
 Polar
Easterlies = wind belts that extend from the
poles to 60o latitude in both hemispheres. These
are formed from cold, sinking are moving from
the poles toward 60o N & 60o S latitude.
•
Northern Hemisphere they blow from the
northeast to the southwest
•
Southern Hemisphere they blow from the
southeast to the northwest.
Page 408
 Jet
Jet Stream
stream = narrow belts of high-speed winds
that blow in the upper troposphere & lower
stratosphere over both the Northern & Southern
Hemispheres.
 These
winds often change their speed & can reach
a maximum speed of 500km/h.
 Unlike
other winds these don’t follow regular
paths around the Earth but change both their
latitude & altitude.
Pages 408 – 409
 These
•
•
Local Winds
are influenced by the geography of an area.
Mountains or shorelines → cause temperature
changes that cause land & sea breezes.
Mountains or shorelines → during the day a
gentle breeze to flow up the slope & at night
cold air flows downslope & settles in the
valley.
Page 410
The Air We Breathe
 Cities
produce pollution. Even as far back as the
Roman Empire cities were producing large
amounts of pollution.
Air Quality
 Natural air pollutants include dust, sea salt,
volcanic gas & ash, smoke from forest fires,
pollen, swamp gas, & many other matters
 Human-caused air pollutants are most
concentrated in cities. The more people the more
pollution there is.
Page 411
Types of Air Pollution
 Primary
pollutants = pollutants that are put
directly into the air by human or natural activity.
• Exhaust from vehicles, ash from volcanic
eruptions, & soot from smoke
 Secondary pollutants = pollutants that form from
chemical reactions that occur when primary
pollutants come in contact with other primary
pollutants or with naturally occurring substances
such as water vapor.
• Automobile exhaust & ozone react in sunlight
& become smog
Page 412
Sources of Human-Caused Air Pollution
source is transportation – cars contribute ≈
60% of the human-caused air pollution in the US.
Industrial Air Pollution
 ≈ 96% of the sulfur oxides released into the air is
given off by industrial plants & electric power
plants.
 The chemicals used by oil refineries, chemical
manufacturing plants, dry-cleaning businesses,
furniture refinishers, & automobile shops all add
poisonous fumes to the air.
 Major
Page 412
Indoor Air Pollution
 Air
pollution is not limited to outdoors. Our
homes, schools, & buildings have air pollution
too. Sometimes the air inside a building is even
worse than the air outside.
 What contributes to air pollution inside:
• Household cleaners, air fresher's, smoke from
cooking, & industrial compounds found in
carpets, paints, building materials, & furniture
Page 413
The Air Pollution Problem
 Pollution
is both a local & global problem because
winds can move pollutants from one place to
another.
 Acid precipitation = precipitation, such as rain,
sleet, or snow, that contains acids from air
pollution.
The Ozone Hole
 In the 1970s scientist determined that some
chemicals being released were reacting with the
ozone in the ozone layer & creating a hole.
Page 414
Effects on Human Health
 Daily
exposure to even small amounts of air
pollution can cause serious health problems.
 Children, elderly people, & people with allergies,
lung problems & heart problems are especially
vulnerable to the effects of pollution.
 It can cause:
• Dizziness, headaches, runny nose, sore throat,
burning, itching eyes, coughing & trouble
breathing, lung cancer & other lung diseases,
chest pains, increased colds, & allergies.
Page 414
Cleaning Up Our Act
 1970
Clean Air Act gives the EPA authority to
control the amount of air pollutants that can be
released from any one source.
 It
checks the air quality & if it worsens then the
EPA can set stricter guidelines.
Page 415
Controlling Air Pollution from Vehicles
 EPA requires
certain standards from car manufactures.
• New cars now have device on the tail pipe that
removes most of the pollutants before exhaust is
released.
• Cars are also moving away from gasoline as a fuel
source.
Controlling Air Pollution from Industry
 Clean Air Act requires the Industry to use scrubbers.
 Scrubber = a device that attaches to smokestacks to
remove some of the more harmful pollutants before
they are released into the air.