Transcript Chapter 6 The Atmosphere

Chapter 6
The Atmosphere
6th Grade
Section 1
 The atmosphere is a mixture of gases that surrounds the
earth.
 It contains the oxygen you breathe and protects us from
radiation from the sun.
 Every breath, tree planted, time you start the car
affects the atmosphere.
Atmosphere
 The atmosphere is made up of mostly nitrogen—78%.
 Oxygen makes up 21% of the atmosphere.
 1% is Argon, Carbon Dioxide, water vapor, and various
other gasses.
 The atmosphere also contains dust, volcanic ash, sea
salt, dirt, and smoke. Water is also present in the
atmosphere. We breathe out water.
Atmosphere
 Air pressure adds up.
 At sea level a square inch surface is under almost 15 lbs
of air. This is the same as carrying a bowling ball on the
tip of your finger.
 As the altitude increases the air pressure decreases.
The atmosphere is held around the earth by gravity.
 Air pressure is the measure of the force with which air
molecules push on the surface. It is strongest at the
surface. WHY???
Atmosphere
 Air temperature also changes as altitude increases. This
is because where gases are located. Different types of
gases absorb heat differently. This is why some parts
are warmer where others are cooler.
Atmosphere
 The atmosphere is divided into four layers.
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Troposphere: where gases turn and mix.
Stratosphere: layered, not much mixing.
Mesosphere: means middle.
Thermosphere: Thermo means heat….where temperatures
are the highest.
Atmosphere
 Troposphere: layer in which we live. It is next to the
earth’s surface. It is the densest atmospheric layer.
Contains 90% of the atmosphere’s total mass. Almost
all of earth’s carbon dioxide, water vapor, clouds, air
pollution, weather, and life forms are in the
troposphere.
 Temperatures vary greatly because of the gases mixing
in the troposphere.
Atmosphere
 Stratosphere: home of the ozone layer
 Gases in this area are layered and do not mix as much
as they do in the troposphere. The air is very thin in
this layer and it contains very little moisture. Lower
stratosphere is very cold -60 C. Temperatures rise as
altitude increases. This rise occurs because ozone in
the stratosphere absorbs ultraviolet radiation from the
sun—this warms the air. The ozone protects life on
earth by absorbing the harmful ultraviolet radiation.
Atmosphere
 Mesosphere: the area above the stratosphere. It is the middle layer
of the atmosphere. It is the coldest layer. Temperatures can be as
low as -93C at the top of the mesosphere.
 Thermosphere: uppermost atmospheric layer. Temperature
increases with altitude. Atoms of nitrogen and oxygen absorb highenergy solar radiation and release thermal energy. The
temperatures can be 1000C or higher. However, it does not feel hot.
Temperature is different from heat. Temperature—average energy of
particles in motion. The particles are moving really fast. Heat is
the transfer of energy from particle to particle. So much space in
the thermosphere the particles do not touch so not much energy is
transferred.
Atmosphere
 Ionosphere: upper mesosphere and lower thermosphere.
Nitrogen and oxygen absorb harmful solar energy. This
causes the temperatures to rise and gas particles
become electrically charged. The electrically charged
particles are called ions. This is why it is called
ionosphere.
 Some areas radiate energy as shimmering lights called
auroras. This is also the area where radio waves reflect
off of and can travel around the world.
Section 2
 Radiation: The earth receives energy from the sun by
radiation. Radiation is the transfer of energy as
electromagnetic waves. The earth only receives about
two-billionths of the energy the sun radiates. This small
fraction is enough to drive the weather cycle and make
earth habitable.
 Conduction: when you touch something hot you have
experienced it. Thermal conduction is the transfer of
thermal energy through a material. It is always
transferred from warmer to cooler areas.
Atmospheric Heating
 50% of the energy from the sun is absorbed by the
earth’s surface.
 20% absorbed by the clouds, ozone, and atmospheric
gases.
 25% is scattered and reflected by clouds and air.
 5% is reflected by the earth’s surface.
Atmospheric Heating
 Convection: Energy transfer by circulation. Ex. watching
a pot of water boil. This is the transfer of thermal
energy by the circulation or movement of a liquid or
gas.
 Cool air sinks and warm air rises. The cool air is
warmed and the process is repeated. Hotter air is less
dense so it rises. This is called convection current. Pg.
157.
Atmospheric Heating
 Greenhouse effect: 70% of radiation that enters earth’s
atmosphere is absorbed by clouds and the earth’s
surface. The energy is converted into thermal energy
that warms the planet. Most of this should escape back
into space. The atmosphere traps it and keeps it within
the earth. This is called the greenhouse effect.
 Greenhouse effect: the warming of the surface and
lower atmosphere of earth that occurs when water
vapor, carbon dioxide, and other gases absorbed and
reradiate thermal energy. It is kind of like the glass
walls and roof of a greenhouse---which prevent solar
energy from escaping.
Atmospheric Heating
 For earth to remain livable the amount of energy received
from the sun and returned to space must be approximately
equal. This balance is known as the radiation balance.
 Many scientist are concerned that temperatures are rising.
This global temperature rise is called global warming.
 The burning of fossil fuels and deforestation are increasing
greenhouse gases—CO2. This rise in temperature could
interrupt climate patterns. Plants and animals that are
adapted to live in specific temperatures could be affected.
However, this debate over this actually occurring is ongoing.
Climate models are extremely complex.
Section 3
 Wind: the movement of air caused by differences in air
pressure.
 The greater the pressure difference and the closer the
pressure systems are to each other the faster the wind
moves.
 Air pressure differences are caused by unequal heating of the
earth.
 Equator: warmer so air rises and creates a less dense area
with lower pressure. Moves towards the poles and lowers. It
is denser so cold air sinks. As the cold air sinks it creates high
pressure.
Air
 Air travels in a large circular pattern. This is called
convection cells. It looks like cells.
 These are separated by pressure belts. This is bands of high
and low pressure found about every 30 degrees latitude.
 As warm air rises and moves toward the poles at about 30
degrees from the equator---30 degrees North and South it
sinks or rises depending on the direction it is traveling. Pg.
161.
 Warm air rising creates low pressure belt.
 Cold air sinking creates high pressure belt.
The Coriolis Effect
 Winds do not travel directly from north or south
because the Earth is rotating.
 Coriolis Effect: the apparent curving of the path of a
moving object from an otherwise straight path due to
the Earth’s rotation.
 Northern hemisphere: winds traveling north curve to the
east and winds traveling south curve to the west.
 http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Ch
p29/animations/ch29/global_wind_circulation.swf
Global Winds
 Air cells and the Coriolis effect produce patterns of air
circulation called global winds. Three major global
winds.
 Polar Easterlies: wind belts that extend from the poles
to 60 degrees latitude in both hemispheres. Formed as
cold, sinking air moves from the poles to 60 degrees
north and 60 degrees south latitude. This is what carries
cold arctic air over the U.S. Blows from the East.
 Westerlies: wind belts from 30 degrees to 60 degrees
latitude in both hemispheres. Carries moist air over the
U.S. to produce rain and snow.
Global Winds
 Trade Winds: in both hemispheres. Blows from 30
degrees latitude and almost to the equator. The Coriolis
effect causes trade winds to curve to the west in the
Northern Hemisphere and to the East in the Southern
Hemisphere. Early sailors used trade winds to sail from
Europe to America.
Trade Winds
 The Doldrums: Trade winds of the Northern and
Southern Hemispheres meet in an area around the
equator. In the doldrums there is very little wind
because of warm, rising air creates a low pressure area.
 The Horse Latitudes: 30 degrees north and 30 degrees
south latitude, sinking air creates an area of high
pressure. Winds are weak. Most of the worlds deserts
are found in horse latitudes.
Winds
 Jet Streams: narrow belts of high speed winds that blow in the upper
troposphere and lower stratosphere. They can blow as fast as 400
km/h. They do not follow regular paths around the earth like global
winds. Jet streams affect the movement of storms. Also helps
pilots. Flying from west to east can be faster than flying east to
west.
 Local winds move short distances and can blow from any direction.
This is caused by temperature differences caused by mountains and
water. Pg. 164
 Mountain and valley breezes. Warm air rises during the day and
moves up mountain slopes. As the air cools it moves down the
mountain and into the valleys.
Section 4
 Air pollution: the contamination of the atmosphere by
the introduction of pollutants from human and natural
sources.
 Primary pollutants: pollutants put directly into the air
by human or natural activities. Ex. dust, volcanic gases,
ash, smoke, pollen, CO, various chemicals.
 Secondary pollutants: when primary pollutants react
with other primary pollutants or naturally occurring
substances. Ozone and Smog are examples.
 Smog=when ozone and vehicle exhaust react with
sunlight.
Human caused air pollution
 Cars-10-20% of human caused air pollution in the U.S.
causes smog and acid rain.
 Industrial air pollution: burns fossil fuels to produce
energy. Oil refineries, chemical manufacturing plants,
dry cleaning businesses, furniture refinishers are
potential sources of air pollution.
 Indoor air pollution: pg. 168.
Air Pollution
 Acid precipitation: rain, sleet, or snow that contains
high amounts of acids. Caused by the burning of fossil
fuels. This burning releases sulfur dioxide and nitrogen
oxide. When they combine with water they form
sulfuric acid and nitric acid.
 Acid precipitation can cause the level of acid in the soil
to increase. This is called acidification. When the acid
level is increased some nutrients the plants need are
dissolved. The acid can also release some toxic metals
to be released and are absorbed by the roots of the
plant.
Acid Precipitation
 Acid precipitation can damage an entire forest. This
can destroy the entire ecology of the forest.
 If acid is increased in aquatic areas everything in the
water may die. Tends to be the worst in the spring
because of melting acid snow. Increases the acid in the
water quickly---this is called acid shock. Some
communities spray lime on acidified lakes which
balances the pH.
 1934
1994
Ozone
 Ozone hole: Thinning of the ozone over the Antarctic.
This is caused by CFCs. Less ozone means that more UV
light rays penetrate. UV radiation damages genes and
causes skin cancer.
 Banned CFCs but they can remain in the stratosphere
for 60-120 years. So they are still destroying the
atmosphere.
 Chlorofluorocarbon
Air Pollution and Human Health
 Pg. 171---read aloud.
 Cleaning air pollution: Clean Air Act was passed by
congress in 1970. It gives the EPA the authority to
control the amount of air pollutants that can be
released from any source---like cars or factories. They
also check air quality.
 Scrubber: a device that is used to remove pollutants
before they are released by smokestacks. Ex. used in
coal burning power plants.