The Atmosphere
• The atmosphere
what is it?
– A thin blanket
of gases that
surrounds the
Earth
• What does it do?
– Controls the weather, water cycle, and
the climate of the Earth.
– Allows for life to exist on Earth
Atmospheric Composition
Atmospheric Composition
Aerosols – solids or tiny
liquid droplets in the
atmosphere other than
gases.
Examples of aerosols:
dust
salt
pollen
volcanic ash
acids
Layers of the Atmosphere
The atmosphere is
divided into the
layers that you see
in this diagram.
These layers are
based on
temperature
changes that occur
with altitude. Each
atmospheric layer
has unique
properties..
Layers of the Atmosphere
• 1. Troposphere - The troposphere is
the atmospheric layer closest to Earth's
surface. It extends upward to about 10
km. The troposphere contains about three
fourths of the matter in Earth's entire
atmosphere and nearly all of its clouds
and weather. Temperatures in the
troposphere are usually warmest near the
surface and tend to cool as altitude
increases.
Stratosphere
STRATO = Layered
• 2. Stratosphere - Above the troposphere is the
stratosphere. The stratosphere extends from
about 10 km to about 50 km above Earth's surface.
Most atmospheric ozone (O3) is contained in the
stratosphere. This ozone absorbs much of the
Sun's ultraviolet radiation. As a result, the
stratosphere warms as you go upward through it,
which is just the opposite of the troposphere.
Without the ozone in this layer, too much radiation
would reach Earth's surface, causing health
problems for plants and animals.
Mesosphere
MESO = Middle
• 3. Mesosphere - Above the
stratosphere is the mesosphere This
layer extends from approximately 50
km to 85 km above Earth's surface.
This layer contains little ozone, so much
less heat is absorbed. The temperature
in this layer drops to the lowest
temperature in the atmosphere.
Thermosphere
THERM = Warm
• 4. Thermosphere - The thermosphere is above the
mesosphere. The thermosphere extends from about 85
km to approximately 500 km above Earth's surface.
Temperatures increase rapidly in this layer to more
than 1,700 C. The thermosphere layer filters out
harmful X rays and gamma rays from the Sun.
– Because of intense interaction with the Sun's
radiation, atoms in this region can become
electrically charged particles called ions. For this
reason a part of the thermosphere and
mesosphere is called the ionosphere. This layer of
ions is useful because it can reflect AM radio
waves, making long-distance communication possible.
Exosphere
EXO = Outer
5. Exosphere - The outermost
layer of the atmosphere is the
exosphere. It extends outward
to where space begins and
contains few atoms. No clear
boundary separates the
exosphere from space.
Energy Balance
Water Vapor
• Water content in the
atmosphere is called the:
humidity
• Composition varies as a
function of temperature.
– Warm air holds > 40 g H2O/Kg
air
– Cold air holds < 5 g H2O/Kg
air
• Addition/removal of water to
the atmosphere
requires/generates energy.
• Importance to climate
– water vapor transfers
heat from warmer to
colder regions
• Latent heat – heat
released or absorbed
when matter changes
state.
Latent
Heat Cycle
Pressure
• Air Pressure – the weight of the overlying air
– Measured in atm or bars (1 bar = 0.986 atm)
– 1 atm is the weight of the atmosphere at sea level ~
1,035 g/cm2
• Mixture of gases in the atmosphere is not uniform
– Air pressure decreases as one moves away from the
Earth’s surface
• As the pressure increases the density of the air
increases
Air Density
Energy and the Atmosphere:
Pressure, Water Vapor, & Weather
• What drives energy within the Atmosphere?
Is the distribution of solar energy equal on the Earth’s surface?
Uneven Heating of Earth Surface
• Solar energy is a function of both
• Location
• Time of year
June 1998 Mean Surface Temperature
What happens to hot air?
• Warm air rises
• As air rises it enters a
lower pressure area and
expands
• Expansion cools the air –
the cold air can hold less
water
• Condensation occurs –
clouds form (latent heat)
Which is more dense cold air or
warm air?
Global Air
Circulation
Where Will
Precipitation and
Evaporation
Occur?
The Atmosphere in Motion
Air masses move
from high
pressure areas to
low pressure
areas
Coriolis Effect
Air Circulation Around a Pressure Low
Low and High Pressure Systems
•
•
•
•
Low Pressure
Air moves up
Weather cloudy
Usually associated
with a cold front
• High Pressure
• Air descending
• Little to no clouds –
sunny
Wave-cyclones & Mid-Latitude
Storms