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Our Atmosphere
Composition
78% Nitrogen remain
21% Oxygen
constant
1% Trace gases, Carbon Dioxide, Water
Vapor, dust
 **concentration water vapor in the
atmosphere varies with the seasons,
 **solids such as dust, ice and salt (picked up
by wind) help the clouds form
Layers of the Atmosphere
 Troposphere -- 0-10 km (closest to Earth)
 Tropo – means “Changing”
We breath this part, planes fly here
Contains the most water vapor
Weather occurs, Most pollution is found
MOST DENSE
The THINNEST
At the top ~temp. lower to -60 C
 Stratosphere -- 10-50 km
Strato- means “spread out”
Made of conc. ozone which
absorbs UV radiation
Ozone layer at about 25 km
Gets heated ( up to 0 C from
-60)
Ozone absorbs harmful rays
from Sun, and converts to
Heat
 Mesosphere -- 50-80 km
Meso- means “middle
layer”
Temperature decreases (-40
to -80 C at top)
Protects Earth from
meteoroids.
Ozone (O3)
 Ground-level ozone is an
air pollutant
*harmful effects on the respiratory
systems of animals
 Ozone in the upper atmosphere filters
potentially damaging ultraviolet light from
reaching the
Earth's surface.
Exosphere – 400+ km
(outermost layer)
 Exo- means “Outer”
 Helium and Hydrogen
 No clear outer boundary
 Satellites found here
Thermosphere -- 100-400 km
 Thermo- means heat
 Very thin layer, solar radiation
absorbed
 Contains “Ionosphere”
 Temperature increases (-80 to
1800 C at the top)
 Aurora Borealis (Northern
Lights) located here.
http://vimeo.com/16917950
Visible
Light and
some
Infrared
get
through
But that’s
NOT all!!!
images are courtesy of Windows to the
Universe, http://www.windows.ucar.edu
So Do Radio Waves!!!!!
Why is the sky blue?
Transmitted light (from sun, light bulbs, fire etc…) is
made of a spectrum of colors – looks white
--Light moves through air --it scatters in all directions
--Longest wavelengths of light = red/orange
Shortest wavelengths = blue/violets
(shorter wavelengths scatter the most light)
--Since blue rays scatter the most,
they reach our eyes from all
directions and we see more
blue than any other color
Atmospheric gases scatter blue light more than
other wavelengths, giving the Earth a blue halo
when seen from space.
What Makes a
Red Sunset?
light has more
atmosphere to pass
through to get to our
eyes, only the strong
red light can make it.
Properties of the Atmosphere



1. Temperature -measures how fast
molecules are moving
(particles in any material =
random motion)
--higher the temp of
material/faster particles are
moving
Temperature inversion:
When warm air is on top of
cooler air
-lack of thermal energy
-smoke, fog, pollution
Conduction
 heat transfer through matter.
 Atoms or molecules must touch each other.
 Type of heat transfer in solids.
 Metals conduct heat well. Air is not a good
conductor of heat.
For example, a spoon in a cup of
hot soup becomes warmer because
the heat from the soup is conducted
along the spoon.
Convection
 heat transfer by the movement of mass from one
place to another.
 Can take place only in liquids and gases .
 Convection occurs when areas of cool dense
molecules and warmer less dense molecules move
near each other.
 The heat moves with the fluid in a
circular pattern because when areas
of cool dense molecules are warmed,
they become less dense and rise.
When areas of warm less dense
molecules move into cooler areas of
molecules, they becomes more dense
and falls.
 Examples: movement of plate,
ocean currents, home furnace
heating & circulating air
Radiation
 Radiation is electromagnetic waves that directly
transport ENERGY through space.
 Sunlight is a form of radiation.
 Radiation is the only way heat is transferred (can
move) through the relative emptiness of space.
 Radiation does not heat air directly as it travels
through the atmosphere from the sun.
 Air is heated by reradiated waves of molecules on
the surface of the earth that absorb energy from the
sun.
Conduction/Convection/Radiation
 Draw
 http://www.wisconline.com/objects/index_tj.asp?objID=SCE304
???
2. Air pressure
 Air has a mass that is constantly
pushing down on us -due to gravity

Pressure is the greatest on the Earths surface and
will decrease as the mass of air above you
decreases

**
Relationship between Air pressure and Temperature
Temperature
Air Pressure
Density of Air
Increases
Increases
Decreases
Decreases
Decreases
increases
3. Humidity
--the amount of water vapor in the air,
-- 2 ways to express water vapor content in
atmosphere:
a) dew point: the temp. in which condensation
occurs
b) relative humidity: the amount of water the air at a
given temp. can hold, expressed in %
Ex. relative humidity is 50%
- air contains 50% of the
water vapor needed
for air to be saturated
Wind



– moving air
--created by an
imbalance between
warm (less dense) &
cool (more dense)
air-creates high/low
pressure areas
--wind speed
increases with height
in atmosphere
Why clouds are white?
Water droplets in clouds
have many surfaces to
Clouds
reflect light, and scatter almost all the light and
look white even though clouds are nearly
transparent
Ex. Root-beer foam, salt/sugar crystal
foam - white / liquid –colored
*walls of the foam bubbles are so thin
– reflect light
while light is absorbed by the liquid
Cloud Formation:
1. Warm, humid air rises
2. Air cools, due to convection
currents
3. Dew point is reached
4. Water droplets form around a
small particle of dust/salt
5. The salt, dust, or ice at the center of the droplet is
called: condensation nucleus
6. If the air mass rises very rapidly, rain occurs


**This can take place at many different altitudes,
which makes different types of clouds
**If it takes place at ground level = fog
Types of Clouds
Luke Howard – 1803
“Man that named the clouds”
3 Main groups
Name of cloud
CirroAltoStrato-
Height of cloud
Above 6000m
2000-6000m
Below 2000m
Each group is then described by shape:
Descriptive name
Cirrus
Curls of hair
Cumulus
Heap
Shape
Wispy stringy clouds
Puffy, lumpy
Stratus
Layer
Sheets of clouds
Nimbus
Rain
Low gray rain clouds
Describe these clouds:

Height and shape are combined to form
name of clouds:
1. puffy clouds at 2000-6000m:
2. low gray clouds below 2000m:
3. above 6000m, wispy clouds:
1. Altocumulus
3. Cirrus
2. Nimbostratus
Vertical Developing Clouds
 Air of cumulus cloud =
 Draw:
unstable
 Cloud warmer than
surrounding air
It will continue to grow upward
 Large, puffy rain clouds =
Cumulonimbus
Can reach past the troposphere
 Result in super-cell
thunderstorms, severe
weather
Precipitation
--All forms of weather that
fall from clouds to ground
Four Main types: Rain,Snow,Sleet, & Hail
Formation of precipitation:
Coalescence – warm cloud droplets collide
and form larger droplets
which are too heavy
to stay aloft
= resulting in Rain
Types of Precipitation
Remember the water cycle song :o)
Snow = in cold clouds ice
crystals are formed
Sleet = convective currents
carry droplets up/down
through freezing &
nonfreezing air, forming
ice pellets
Hail = if up/down motion is
extremely strong & takes
place over long stretches
of atmosphere, forms
very large ice pellets
The End
 http://www.williamsclass.com/EighthScience
Work/Atmosphere/EarthsAtmosphere.htm
 http://starryskies.com/solar_system/Earth/at
mosphere.html
