18.1
 Made
up of mainly two
gases:
–Nitrogen 78%
–Oxygen 21%
–Trace Gases 1%
 made
up of 5 layers:
– Troposphere
– Stratosphere
– Mesosphere
– Ionosphere
– Thermosphere
The atmospheric layer we live in.
 Almost all weather occurs here.
 Contains water vapor and oxygen.
 Highest density
 Temps decrease as you increase
altitude until you reach the top of
the layer called the tropopause.

Within the troposphere a
temperature inversion may occur.
 This is a condition where warmer
air traps cooler air near the Earth’s
surface.
 This can cause air to get thick with
pollution, where it can’t escape.

– Lacks O2 and water vapor. (no
– Contains the ozone (O3) layer.
weather)
(this layer absorbs solar UV radiation)
– Temperatures increase as you gain
altitude.
– Higher altitude than most aircraft would
fly
–The
coldest of layer of the
0
atmosphere. (-80 C)
–Temperature decreases
with altitude




Consists of upper mesosphere and lower
thermosphere.
Contains charged ions that reflect radio waves
allowing transmissions to travel great distances.
Radio waves will travel farther at night than
during the day. (less ions)
Where the aurora borealis can be seen. (excited
photons)
 Most
outer layer.
0
 Hottest layer (980 C)
 temperatures will increase
with increase altitude
 It absorbs solar radiation
 Early
atmosphere was much
different during Earth’s early
days.
 Volcanic eruptions released H2,
ammonia, methane. CO, CO2 and
N2.
 No oxygen was present
Around 2.5 billion years ago single
celled organisms evolved to capture
the suns energy and CO2 to start the
photosynthesis process
 Then plants began appearing
releasing oxygen into the
atmosphere.

350 million years later aerobic
organisms came along and
balanced the atmosphere.
 They took in oxygen and released
carbon dioxide as a by product
during respiration.
 And thus the O2 and CO2 cycle was
created.

Protects us from UV radiation.
 Can be destroyed by
chlorofluorocarbons or CFC’s
 Used during 1950s thru 1980s in
refrigerators and spray cans.
 CFCs are now banned in most
countries
 Ozone layer is repairing itself

 Ozone
while helpful in
stratosphere, is very toxic
if trapped in the
troposphere.
 Main gas pollutant from
cars, trucks, factories that
causes smog.
 The
process by which the
atmosphere traps some of the
energy from the sun in the
troposphere.
 CO2, water vapor, and other
gases absorb the suns energy
(greenhouse gases)
 Keeps the planets climate
balanced

We are adding more and more CO2 and
other greenhouse gases into the
atmosphere:
– Forest fires and volcanoes
– Air Pollution from fossil fuel burning
– Increasing human population
– Decrease in plant life and rain forest
– Increase of cattle grazing
18.2
The
continuous movement
of water from atmosphere
to Earth and back.
 4 mechanisms of travel
 Water
enters the atmosphere:
1. Evaporation
 Evaporation occurs at the lakes,
rivers, and oceans.
2. Transpiration
 evaporation of water through
plant’s leaves.
Water Exits:
3. Condensation
 Water vapor rises until it is cool enough
to condense to form clouds.
4.
Precipitation
 When the cloud become full of water
droplets they will release moisture back
down to Earth in the form of rain, sleet,
ice, or snow.
Condensation
Evaporation
Water vapor is always in the air
 Humidity
– The quantity/amount of water
vapor in the atmosphere
 Relative humidity (percentage)
– is the actual amount of water in the
atmosphere compared to
maximum amount it can hold.
 The higher the temperature, the
more water that can be held in the
air.

 The
temperature at which
water vapor molecules start to
form liquid water.
 Higher the humidity the
higher the dew point.
 dew point
Made
up of tiny
condensed droplets of
liquid water.
 3 main types
highest
altitude clouds
appear wispy and light.
 layered
or sheet like
clouds
 form at lower altitudes.
white
and fluffy
appear at many levels.
 Other
clouds are a combination
of the 3 cloud types.
 The root nimbus means the
cloud contains precipitation.
(grayer color)
 Ex. cumulonimbus produce
thunderstorms
 The
pressure due to the
weight of the atmosphere.
 Measured with an instrument
called a barometer.
 Air pressure decreases with
altitude in the troposphere
 Caused
by differences in air
pressure between air masses.
 The greater the difference the
stronger the wind.
 Air always flows from high
pressure to low pressure
– Pressure
inside a plane is greater,
so air would be sucked out if a
window broke
 Coriolis
effect.
the change in direction of
an object’s path due to
Earth’s rotation.
 Winds
in the Northern
hemisphere curve right.
 Winds in the southern
hemisphere curve left.
18.3
 The
condition of the atmosphere
at any given time
 Weather is caused by traveling
air masses.
– Large bodies of air with the
same general characteristics
throughout.
A
boundary where two
air masses with different
densities meet.
 Fronts cause
precipitation, change in
temperature, and a
change in wind direction.
Warm
front
-warm air moves over
cooler air forming clouds.
-Produces steady rain or
snow for a couple of days.
Cirrus and cirrostratus
clouds
 Cold
fronts
-Cold air moves under slow
moving warm air
-Brings high winds,
thunderstorms, and
possible tornadoes.
Cumulonimbus clouds
 Two
air masses meet
 Neither is displaced
 Air masses move side by side
 Similar to warm front
weather
Lightening is caused by a build up of
electrical charges from water
droplets and ice crystals in clouds.
 When opposite charges are found on
the ground or other clouds,
lightening strikes.
 Thunder is the sound of lightening.

 If
you count to 10 or less
after seeing lightning
before hearing thunder,
then the storm is less than
two miles away.

Form during severe thunderstorms.
 Form
from cool air from the north,
and warm air from south.
Tornadoes begin as a funnel cloud that
intensifies until it touches ground
 Most violent winds on Earth 310mi/hr

 Most
common in the Midwest
 Very
large storms with high
winds.
 Also known as cyclones and
typhoons
 Form in the tropics
 Created by rising warm water
vapor from warm ocean water.
 Then powered by the energy
released from water vapor
condensing into clouds
 Produced
by meteorologists to
help forecast weather.
 They use many variables
– Precipitation and cloud cover
– Wind speed
-Air pressure (isobars)
– fronts
Average weather
condition over many
years for a particular
region.
 It is not measured day by
day.

1.
Latitude (closeness to equator)
 Angle at which the sun hits Earth
2.
Cycling of seasons and season Length
 The tilt of the earth’s axis as it travels a
revolution around the sun is the reason
that we have seasons.
3.
4.
Yearly rainfall
Topography (type of land)
 Elevation, amount of water, mountains or
flatness