The Atmosphere

1
Chapter 3

• Section 2

2
The Atmosphere

• Earth is surrounded by a mixture of gases called
  the atmosphere.
• Nitrogen (78), oxygen (21), carbon dioxide, and
  other gases are all parts of this mixture.

3
Composition of the Atmosphere

• In addition to gases, the atmosphere contains
  many types of tiny, solid particles (atmospheric
  dust)
• Atmospheric dust is mainly soil, but includes
  salt, skin, hair, bits of clothing, pollen,
  bacteria and viruses, and tiny, liquid droplets
  called aerosols.

4
Air Pressure

• Earths atmosphere is pulled toward Earths
  surface by gravity.
• As a result, almost the entire mass of Earths
  atmospheric gases is located within 30 km of our
  planets surface.

5
Layers of the Atmosphere

• The atmosphere is divided into four layers based
  on temperature changes that occur at different
  distances above the Earths surface.

6
Troposphere

• Earths densest layer
• Closest to Earths surface
• Temp. decreases as altitude increases
• Where weather occurs

7
The Stratosphere

• The stratosphere is the layer above the
  troposphere.
• It extends from 18 km to about 50 km.
• Temperatures rise as altitude increases, because
  ozone in the stratosphere absorbs the suns
  ultraviolet energy and warms the air.

8
Ozone

• Ozone is a molecule that is made up of three
  oxygen atoms.
• Almost all the ozone in the atmosphere is
  concentrated in the ozone layer in the
  stratosphere.
• Since ozone absorbs UV radiation, it reduces the
  amount of UV radiation that reached the Earth. UV
  radiation that reaches the earth can damage
  living cells.

9
The Mesosphere

• The layer above the stratosphere is the
  mesosphere, which reaches an altitude of about 80
  km.
• It is the coldest layer of the atmosphere, with
  temperatures as low at -93C.

10
The Thermosphere

• The thermosphere is the layer that is located
  farthest away from the Earth.
• In the thermosphere, nitrogen and oxygen absorb
  solar radiation, which results in temperatures
  that have been measured about 2,000C.

11
Energy in the Atmosphere

• Radiation is the transfer of energy across space
  and in the atmosphere.
• Conduction is the flow of heat from a warmer
  object to a colder object.
• Convection is the transfer of heat by air
  currents.

12
Heating of the Atmosphere

• Solar energy reaches the Earth as electromagnetic
  radiation, which includes visible light, infrared
  radiation and ultraviolet light.
• The sun releases a vast amount of radiation, but
  our planet only receives about two-billionths of
  this energy.

13
The Movement of Energy in the Atmosphere

• Air that is constantly moving upward, downward,
  or sideways causes Earths weather.
• The continual process of warm air rising and cool
  air sinking moves air in a circular motion,
  called a convection current.

14
The Greenhouse Effect

• When the earth's atmosphere traps solar
  radiation, caused by gases such as carbon
  dioxide, water vapor, and methane.
• These gases allow incoming sunlight to pass
  through but absorbed heat cannot re-radiate back
  into the atmosphere.