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The envelope of gas surrounding the Earth changes from the ground up.
Five distinct layers have been identified using...
·thermal characteristics (temperature changes),
·chemical composition,
·movement, and
Each of the layers are bounded by "pauses" where the maximum changes
in thermal characteristics, chemical composition, movement, and density
The layers are troposphere, stratosphere, mesosphere, thermosphere,
and exosphere.…read more

Slide 3

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The troposphere begins at the
Earth's surface and extends up to
4-12 miles (6-20 km) high. This is
where we live. As the density of
the gases in this layer decrease
with height, the air becomes
thinner. Therefore, the
temperature in the troposphere
also decreases with height. As you
climb higher, the temperature
drops from about 62°F (17°C) to
-60°F (-51°C). Almost all weather
occurs in this region.
The transition boundary between
the troposphere and the layer
above is called the tropopause.
Together the tropopause and the
troposphere are known as the
lower atmosphere.…read more

Slide 4

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The Stratosphere extends from the tropopause
up to 31 miles above the Earth's surface. This
layer holds 19 percent of the atmosphere's
gases but very little water vapor.
Temperature increases with height as radiation
is increasingly absorbed by oxygen molecules
leading to the formation of Ozone. The
temperature rises from an average -76°F (-60°
C) at tropopause to a maximum of about 5°F
(-15°C) at the stratopause due to this
absorption of ultraviolet radiation. This
increase is temperature with height means no
"convection" occurs since there is no vertical
movement of the gases.
The transition boundary which separates the
stratosphere from the mesosphere is called
the stratopause. The regions of the
stratosphere and the mesosphere, along with
the stratopause and mesopause, are called the
middle atmosphere by scientists.…read more

Slide 5

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The mesosphere extends from the
stratopause to about 53 miles (85 km)
above the earth. The gases, including the
oxygen molecules, continue to become
thinner and thinner with height. As such,
the effect of the warming by ultraviolet
radiation also becomes less and less leading
to a decrease in temperature with height.
On average, temperature decreases from
about 5°F (-15°C) to as low as -184°F (-120°
C) at the mesopause.
However, the gases in the mesosphere are
still thick enough to slow down meteorites
hurtling into the atmosphere, where they
burn up, leaving fiery trails in the night sky.…read more

Slide 6

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The Thermosphere extends from the mesopause to
430 miles (690 km) above the earth. This layer is
known as the upper atmosphere.
The gases of the thermosphere are increasingly
thinner than in the mesosphere. As such, incoming
high energy ultraviolet and x-ray radiation from the
sun, absorbed by the molecules in this layer, causes a
large temperature increase.
Because of this absorption, the temperature
increases with height and can reach as high as 3,600°
F (2,000°C) near the top of this layer; however,
despite the high temperature, this layer of the
atmosphere would still feel very cold to our skin
because of the extremely thin air. The total amount
of energy from the very few molecules in this layer is
not enough to heat our skin.…read more

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