Transcript Atmospheric Layers

Earth’s Atmosphere
• The Earth is surrounded by a blanket of air
called the atmosphere.
• It extends over 372 miles (560 kilometers)
from the surface of Earth
• It protects us from high-energy radiation and
the frigid vacuum of space
• The atmosphere absorbs energy from the Sun,
recycles water and other chemicals and works
with the electrical and magnetic fields of Earth
to provide a moderate climate
Composition of the Atmosphere
• The atmosphere is
made up of a mixture
of atoms and molecules
of different kinds of
gases
• Each type of gas has
important uses and
roles for our planet
• Nitrogen, oxygen and
argon are the primary
components
• There are other very influential components
including water, “greenhouse” gases or ozone and
carbon dioxide
Layers of the Atmosphere
• Four distinct layers have been identified
using temperature changes, chemical
composition, movement and density:
Troposphere
Stratosphere
Mesosphere
Thermosphere
Layers of the Atmosphere
The Troposphere
• The troposphere starts at the Earth’s surface
and extends more than 9 miles above the
equator to less than 5 miles above the North
and South Poles
• Tropo means “turning” or “changing”
• Most dense part of the atmosphere
• As you climb higher, the temperature drops
from about 17 to -52° C
• Almost all weather occurs at levels below 10
miles
The Stratosphere
• The stratosphere extends from the top of the
troposphere to about 31 miles above Earth’s
surface
• Strato is similar to stratum which means “layer”
or “spreading out”
• The lower stratosphere is –60° C
• The upper stratosphere is actually warmer than
the lower stratosphere because of a thin layer
of ozone, which absorbs energy form the sun
which is converted to heat
The Mesosphere
• Above the stratosphere, a drop in temperature
marks the beginning of the next layer, the
mesosphere
• Meso means “middle”
• It begins about 31 miles above Earth’ surface
and ends at approximately 53 miles high.
• The outer mesosphere is the coldest part of the
atmosphere, with temperatures near - 90° C
The Thermosphere
• The outermost layer is called the thermosphere,
which extends from about 53 miles above
Earth’s surface outward into space.
– It is actually divided into two separate layers:
Ionosphere and Exosphere
• Thermo means “heat”
• The air is very thin in the thermosphere and
extremely hot, up to 1800° C
The Thermosphere
• The lower layer of the thermosphere is called
the ionosphere and begins about 53 miles
above Earth’s surface and ends around 372
miles
• Energy from the sun causes gas molecules to
become electrically charged particles called
ions
– Radio waves bounce off these ions and back
to the Earth
• The brilliant light display of the aurora borealis
(Northern Lights) also occurs in the ionosphere
The Thermosphere: Exosphere
• The upper layer of the thermosphere is
called the exosphere and extends from
372 miles outward for thousands of miles
• Satellites orbit in the exosphere
Energy in the Atmosphere
Most of the energy that keeps Earth warm comes
from the Sun. Some of this energy is reflected or
absorbed in the atmosphere. The rest reaches Earth’s
surface, where it is reflected or absorbed
Clouds, dust and gases
in the atmosphere
reflect and scatter light
Solar energy is mostly
visible light and
infrared radiation, and a
small amount of
ultraviolet radiation
Gases and particles in
the atmosphere absorb
solar energy
Some energy that
reaches the surface is
reflected back into the
atmosphere
Some of the absorbed energy is
then radiated back into the
atmosphere
Earth’s surface absorbs
solar energy. This energy
heats the land and water
Heat Movement in the
Troposphere
• Radiation, conduction and
convection work together to
heat the troposphere.
• When Earth’s surface
absorbs solar energy during
the day, the surface
becomes warmer than the
air.
• The air near the Earth’s
surface is warmed by
radiation and conduction of
heat from the surface to the
air.