Download Earth*s Atmosphere

Earth’s Atmosphere
Why is it important?
 Without its atmosphere, Earth would be a very
different planet.
 Gases in the atmosphere allow:
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plants to photosynthesize
animals and plants to engage in respiration.
Water Cycle
 Role of the atmosphere:
 Water vapor, which is an atmospheric gas, is an essential part
of the water cycle.
Weather
 All weather takes place in the atmosphere.
 Weather describes what the atmosphere is like at a
specific time and place.
 Changes day to day.
 This can include:
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Temperature
Wind
Precipitation
Climate
 Climate is the long-term average of weather in a
particular spot.
 Example:
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Weather for a particular winter day in Tucson, Arizona, may
include snow, however, the climate of Tucson is generally
warm and dry.
Ozone
 Ozone is a molecule composed of three oxygen
atoms, (O3).
 Located in the upper atmosphere.
 Absorbs high-energy ultraviolet (UV)
radiation coming from the Sun.

Without ozone for protection, only the simplest life forms
would be able to live on Earth.
Atmospheric Gases
 Keep Earth's temperatures within an acceptable
range.
 Greenhouse gases trap heat in the atmosphere so
they help to moderate global temperatures.
 Without an atmosphere with greenhouse gases,
Earth's temperatures would be frigid at night and
scorching during the day.
 Important greenhouse gases include:
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carbon dioxide, methane, water vapor, and ozone.
Composition of Air
 Nitrogen and oxygen make up 99% of the
atmosphere.
 Carbon dioxide and water vapor are very important ,
but a minor component.
Humidity
 Humidity is the amount of water vapor in the air.
 Equatorial regions have higher humidity
 Air temperatures are higher and warm air can hold more
moisture than cooler air.
 Humidity is lower near the polar regions because air
temperature is lower.
Atmospheric Pressure
 Air pressure is the force of air weighing down over a
unit of area.
 At higher altitudes, air pressure is lower.
This bottle was closed at an
altitude of 3,000 meters where air
pressure is lower. When it was
brought down to sea level, the
higher air pressure caused the
bottle to collapse.
Layers of the Atmosphere
 Troposphere
 Stratosphere
 Mesosphere
 Thermosphere
 Exosphere
Layers of the Atmosphere
 Divided into layers based on how the temperature in
that layer changes with altitude.
 The temperature gradient in each layer is
determined by the heat source of the layer.
 The layers of the atmosphere appear as different colors in
this image from the International Space Station.
Troposphere
 The lowest layer that is closest to Earth’s surface.
 Where most of the atmospheric gases are located.
 All of the planet’s weather
occurs here.
 Heated from the ground,
so temperature decreases
with altitude.
Because warm air rises and cool air
sinks, the troposphere is unstable.
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Temperature Inversion
 When air temperature increases with altitude.
 Warm air sits over cold air.
 Inversions form:
 Over land at night or in winter when the ground is cold.
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The cold ground cools the air that sits above it, making this low
layer of air denser than the air above it.
Near the coast where cold seawater cools the air above it.
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When that denser air moves inland, it slides beneath the warmer
air over the land.
Thermal Inversion
 Since temperature inversions are stable, they often trap
pollutants and produce unhealthy air conditions in cities.
Stratosphere
 Temperature increases with altitude.
 Contains the ozone layer, which protects the planet
from the Sun’s harmful UV radiation.
 The Sun is the direct heat source for the
stratosphere.
 Air in the stratosphere is stable
because warmer, less dense air
sits over cooler, denser air.
As a result, there is little mixing of
air within the layer.
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 Even with the ozone layer, UVB radiation still manages to
reach Earth's surface, especially where solar radiation is
high.
Mesosphere
 Temperatures decrease with altitude.
 Few gas molecules in the mesosphere to absorb the
Sun’s radiation.
 Heat source is the
stratosphere below.
 Meteors burn in the mesosphere even though the gas is
very thin; these burning meteors are shooting stars.
Thermosphere
 The density of molecules
is so low that one gas
molecule can go about 1
km before it collides with
another molecule.
 Since so little energy is
transferred, the air feels
very cold.
Ionosphere
 Located within the Thermosphere.
 Contains ionized particles due to solar radiation.
 When the Sun is active, more ionization occurs.
 Makes long distance radio communication possible.
Magnetosphere
 The magnetic field of the Earth is surrounded in a
region called the magnetosphere.
 Prevents most of the particles from the sun, carried
in solar wind, from hitting the Earth.
Solar Wind
 Beyond the atmosphere.
 Made of high-speed particles
 mostly protons and electrons, traveling rapidly outward from
the Sun.
Aurora
 The particles from solar wind that enter the
magnetosphere create the aurora lights.
 Different elements give off different colors.
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Oxygen= green (sometimes red)
Nitrogen= red, blue and purple
Exosphere
 The outermost layer of the atmosphere.
 Gas molecules are so scarce that at some point there
are no more.
Imagine Earth with No Atmosphere
 What happened to Mars?