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The Atmosphere
Earth’s Thin Blue Skin
The Atmosphere
• The atmosphere is a mixture of gases that
surrounds a planet, such as Earth.
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Nitrogen(78.4%)
oxygen (21%)
carbon dioxide (0.03%)
Argon (1%)
Water vapor (up to 4%)
Other gasses
The Atmosphere
• The atmosphere insulates Earth’s surface.
• Greenhouse effect- keeps Earth’s
temperatures in the zone for life
Layers of The Atmosphere
• The atmosphere is divided into four
layers based on temperature changes
that occur at different distances above
the Earth’s surface.
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The Troposphere
The Stratosphere
The Mesosphere
The Thermosphere
The Troposphere
• The troposphere is the lowest layer of the
atmosphere in which temperature drops at
a constant rate as altitude increases.
• We live in the troposphere.
• This is the part of the atmosphere where
weather conditions exist.
• The troposphere is Earth’s densest
atmospheric layer and extends to 18 km
above Earth’s surface.
The Stratosphere
• The stratosphere is the layer of the
atmosphere that lies immediately above
the troposphere and extends from
about 10 to 50 km above the Earth’s
surface.
• Contains ozone layer.
Ozone
• Ozone is a gas molecule that is made up
of three oxygen atoms.
• Absorbs UV radiation, it reduces
amount of UV radiation that reaches
the Earth.
• UV radiation that does reach Earth can
damage living cells.
• OZONE HAS NOTHING TO DO WITH
GLOBAL WARMING!!!!!
The Mesosphere
• The layer above the stratosphere is the
mesosphere.
• This layer extends to an altitude of
about 80 km.
• This is the coldest layer of the
atmosphere where temperatures have
been measured as low as
–93ºC.
The Thermosphere
• The atmospheric layer located farthest from
Earth’s surface is the thermosphere.
• Here, nitrogen and oxygen absorb solar
radiation resulting in temperatures measuring
above 2,000 ºC.
• The air in the thermosphere is so thin that
air particles rarely collide, so little heat is
transferred, and would therefore not feel hot
to us.
Heating of the Atmosphere
• About half of the solar energy that enters
the atmosphere passes through it and reaches
the Earth’s surface, while the rest of the
energy is absorbed or reflected in the
atmosphere by clouds, gases, and dust or it is
reflected by Earth’s surface.
Heating of the Atmosphere
• The Earth does not continue to get warmer because
the oceans and the land radiate the absorbed energy
back into the atmosphere.
• Because the ocean both absorbs and releases heat
slower than land, the temperature of the atmosphere
changes more slowly.
• This is one reason the temperature in cities is higher
that the temperature in the surrounding countryside.
• Heating of the air is not even everywhere!
Movement of Air in the Atmosphere
• As a current of air, warmed by Earth’s
surface, rises into the atmosphere, it
begins to cool, and eventually becomes
more dense than the air around it and
sinks. This current then moves back
toward the Earth until heated and less
dense and then begins to rise again.
• The continual process of warm air rising
and cool air sinking moves air in a
circular motion is called a convection
current.
Weather
 Temporary behavior of atmosphere
(what’s going on at any certain time)
 Small geographic area
 Can change rapidly
Climate
 Long-term behavior of atmosphere
(100+ years)
 Large geographic area
 Very slow to change
Air Masses
• body of air with a certain
temperature and moisture level
• As it moves, the characteristics
of an air mass change and so does
the weather
Fronts
• places where air masses meet
• 4 Types: Warm, Cold, Occluded,
Stationary
• Each kind can bring different
kinds of weather
Fronts
• Cold Front – cold,
dense air moves
into a region
occupied by warmer
air, leads to heavy
downpours and
gusty winds
• Warm Front –
warm air moves
into an area
occupied by cooler
air, Brings warmer
temperatures and
precipitation,
Fronts
• Occluded Front –
an active cold front
takes overtakes a
warm front;
complex weather
pattern
Occluded Front
• Stationary Front –
flow of air is neither
toward cold or warm
air mass.
Stationary
Front
Pressure Differences Move Masses
• Air has mass.
• The weight of air at the surface causes
pressure.
• Warm air rising creates a low pressure.
• Cold air sinking creates a high pressure.
Low pressure
• Moisture of rising air condenses causing
clouds.
• Wind moves counter clockwise.
High Pressure
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Cool dry air sinks causing clear weather.
Air moves clockwise.
Usually light winds
Represented with an H on the map
Moisture in the air
• Warm air can hold more moisture than cold
air.
• Relative humidity is how close to SATURATED
the air is.
• Dew point is the temperature the moisture in
the air will condense to liquid water.
• Higher dew point= more humid. (Above
Dew point and human comfort
Dew point F°
Over 80
Human Comfort
Severely high. Even deadly
for asthma related illnesses
75-79
70-74
65-69
60-64
55-59
50-54
Less than 49
Extremely uncomfortable
Quite uncomfortable
Somewhat uncomfortable
Ok, but feels humid
Comfortable
Very comfortable
Dry
Human Impact on the
Atmosphere
Air pollution
Human activity produces two main types of air
pollutant:
 noxious gases – Include carbon dioxide (CO2), sulfur
dioxide (SO2) and nitrogen oxides (NOx).
 particulates – Tiny particles suspended in air (e.g.
smoke) and are usually produced by the combustion of
fossil fuels.
Air pollution has been a major problem since the
Industrial Revolution of the late 18th Century, and has
been made worse by humans’ reliance on burning fossil
fuels for energy.
Air pollution, global warming, acid rain, damage to the
ozone layer and smog. Each of these has serious
implications for the environment and human health.
Greenhouse Effect
• The greenhouse effect is the warming
of the surface and lower atmosphere of
Earth that occurs when carbon dioxide,
water vapor, and other gases in the air
absorb and reradiate infrared radiation.
• Without the greenhouse effect, the
Earth would be too cold for life to
exist.
Greenhouse Effect
• The gases in the atmosphere that trap and
radiate heat are called greenhouse gases.
• The most abundant greenhouse gases are
water vapor, carbon dioxide, methane, and
nitrous oxide, although none exist in high
concentrations.
• The quantities of carbon dioxide and methane
in the atmosphere vary considerable as a
result of natural and industrial processes.
Global warming and
greenhouse gases
One of the greatest threats caused by air pollution is
global warming. Global warming is caused by a build-up of
greenhouses gases, which leads to an increase in the
Earth’s temperature. Other effects include bizarre
weather patterns, and melting of polar ice caps
Key greenhouses gases include:
 carbon dioxide
 methane
 water vapour
 nitrous oxide
Acid Precipitation
• Caused by the
release of sulfur
dioxide and nitrogen
oxide from factories
• Effects include soil
erosion, death of
animals and
vegetation, erosion
of buildings
Ozone Depletion
• Caused by the use of
coolants and aerosol
cans
• Effects include
increased UV
radiation, skin
cancer and eye
disorders
Smog
Smog is a mixture of air pollutants and particulates that
is sometimes found in the lower levels of the
atmosphere. It has a distinctive brownish haze.
Smog can reach
dangerous levels in builtup areas, causing
irritation to the eyes and
lungs.