1. The Atmosphere

2. What is the atmosphere?
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The thin layer of gases that
surrounds our planet.
Weather is the condition of
the atmosphere at a certain
place and time.
Our atmosphere makes life
possible on our planet.
Provides us with oxygen.
Keeps surface warm so water
can exist as a liquid.
Protects the surface from
dangerous radiation from the
sun.
Protects us from most
meteoroids or rocks from
space.

3.  Weather :
state of
atmosphere at any given
time and place
– temperature
– precipitation
– air pressure
– wind
– humidity

4. Climate
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Aggregate (average) of weather
conditions over a long period of time.
– Example: A place that doesn't get much
rain over many years would have a dry
climate. A place where it stays cold for
most of the year would have a cold climate.
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Look out your window any day, any
time and you see weather. Look out
your window every day for a month or
longer, observe the weather each day,
and you can determine the climate.

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The Composition of the
Atmosphere
Nitrogen makes up 78% of our atmosphere
Oxygen makes up 21%
Argon makes up almost 1%
All other gases have only trace amounts

6. Trace elements/compounds
Carbon dioxide: plants use to produce
food. Plants take in CO2 and give off
oxygen as a waste product.
 Animals take in oxygen to make energy
and give off CO2 as a waste product.
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Fossil fuels (coal, oil, natural gas) give
off CO2 when they are burned. Rising
CO2 levels may cause global warming.
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The fizz in soda is really CO2 bubbles.
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Dry ice is CO in the solid state.

7. Ozone
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Ozone is a molecule of
oxygen with 3 oxygen atoms
instead of 2.
Often formed when
lightning interacts with
oxygen in the air or by UV
rays in the upper
atmosphere.
Forms a layer in the
atmosphere that absorbs
ultraviolet radiation from
the sun. Without this layer
life might not be possible on
the surface of the planet.

8. Earth’s Early Atmosphere
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The Precambrian atmosphere was
composed mainly of nitrogen and carbon
dioxide, along with some methane and
ammonia.
Volcanoes spewed water vapor, carbon
monoxide, and even more nitrogen and
carbon dioxide into the air. Comets also
contributed water vapor, but no free
oxygen.
So where did the abundant oxygen that
has made life as we know it come from?

10. Precambrian Life
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The first life on Earth was
cyanobacteria (like single
celled blue-green algae).
They used photosynthesis to
turn CO2 into the food and
energy they needed to
survive.
Photosynthesis gives off
oxygen as a waste product.
So over the millions of
years, oxygen given off by
algae built up in the
atmosphere, while the
amount of CO2 declined.

11. Layers of the
Atmosphere

12. Pressure
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Pressure is a force that acts
over a certain area.
Liquids and gases are fluid. Fluid;
are any material that is able to
flow. Fluids exert pressure
because of the motion of their
particles.
Pressure will always move from a
high pressure to a low pressure
area. The pressure will always
try to equalize. You see this
when you get a hole in your
bicycle tire.

13. Air Pressure
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Air pressure is the
result of the column
of air that is above
you.
There is so much air
above you that at sea
level you have 14.7
lbs/in2 pushing on you.
Gravity causes most
of the air to be pulled
down to the surface.

14. Why are we not crushed
by air pressure?
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Air pressure is
equal in all
directions.
So air pushes
equally in all sides
of us. The forces
are balanced!

16. Units of Air Pressure
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TV weather stations
and aviation use
inches of mercury.
Meteorologists (and
the NWS) use
millibars, an SI unit.

17. Altitude and Density
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As the air pressure
decreases, the density of
the air decreases. The
air particles are not
squashed together as
tightly the higher one
goes. This is caused by
gravity!
The air at sea level and
at 6km has the same 21%
oxygen, but at 6km there
are fewer molecules, so
you take in less oxygen
with each breath.

19. Temperature and the
Troposphere
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Troposphere:
temperature at surface
is warmed by the earth
absorbing energy from
the sun .
Convection currents
carry the heat upward,
so the air cools as it
rises.
The air cools by about
6.5°C for every 1-km
above the ground.

20. Temperature and the
Stratosphere
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Ozone absorbs
ultraviolet radiation
from the sun, causing
the temperature to
increase.

21. Temperature and the
Mesosphere
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This layer does not
absorb energy
from the sun, so it
starts to cool
again.
Without
greenhouse gases,
energy pretty
much passes
straight through!

22. Temperature and the
Thermosphere
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Solar radiation first hits
this layer, so the few
particles that are here can
gain lots of energy. They
move rapidly, so they have a
very high temperature.
But the air is so thin here
that it takes special
instruments to measure the
temperature accurately.
So even though it is very
hot (over 1000°C), it would
feel cold because there are
so few particles to transfer
heat to you.

23. The Troposphere
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Lowest (inner) layer
weather occurs here
we live in it.
“tropo” means turning
or changing conditions
depth varies from 9km
above the poles to 16km
at the equator
thinnest layer, but
contains most of the
mass (90%).

24. The Stratosphere
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“strato ” means layer
or spreading out
Contains the ozone
layer which absorbs
energy and causes the
temperature to rise
The ozone layer
protects the surface
from dangerous UV
rays

25. The Mesosphere
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Drop in
temperature
marks beginning of
mesosphere
“Meso” means
middle
Most meteors
burn up here

26. The Thermosphere
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Very top layer
Air is very, very thin, about
1/1000th as dense as the air at
sea level
“Thermo” means heat
Extends from 80km to space
No definite outer edge
Very hot (over 1000°C), but
since air is so thin it would not
feel warm at all.
Divided into two parts, the
ionosphere and the exosphere

27. The Ionosphere
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Energy from sun strips the
electrons from the gas
molecules creating charged
particles called ions.
Radio waves can bounce off of
ions, allowing radio waves to
travel great distances.
The aurora borealis (Northern
Lights) occur here

28. The Exosphere
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“Exo” means outer
Extends for 1000’s
of miles
Satellites orbit
here
No definite edge
Molecules
gradually escape
out into space