The Atmosphere

1
The Atmosphere

• Atmosphere mixture of gases that surround the
  Earth
• Gases include nitrogen, oxygen, carbon dioxide,
  and others
• Animals remove oxygen and add carbon dioxide
• Plants remove carbon dioxide and add oxygen
• Volcanic eruptions add gases
• What else?
• Atmosphere insulates the Earths surface
• This slows the speed that heat is lost
• it keeps the Earth at temperature for survival

2
Composition of the Atmosphere

• 78 is nitrogen
• Comes from volcanic eruptions
• Comes from decaying plants and animals
• 21 is oxygen
• Produced by plants
• 1 is mixture of argon, carbon dioxide, methane,
  water vapor
• Also in atmosphere is atmospheric dust many
  different, tiny solid particles
• Includes soil, salt, fire ash, volcanic ash,
  skin, hair, pollen, bacteria viruses etc.

3

• Air pressure- gravity pull on atmosphere
• More gases particles are located closer to
  Earth
• Higher in the air, less particles and gases
• Almost all the mass of atmosphere is located
  within 30 km of earth surface
• Why is it harder to breather as you go higher in
  air?
• 4 Layers of Atmosphere
• Layers based on temperature changes at different
  distances above Earth
• Troposphere layer nearest the Earths surface
• Extends about 18 km above earth surface
• Almost all weather occurs in this layer
• Temperature decreases as altitude increases
• Most particles located in troposphere

4

• Stratosphere extends from about 18 km to 50 km
  above earth surface
• Temperature RISES as altitude increases
• Ozone layer absorbs the suns ultraviolet (UV)
  energy and warms the air
• Ozone, O3- molecule made of 3 oxygen atoms
• Ozone layer- area where almost all ozone is
  located that absorbs UV rays
• Protects life on earth from harmful radiation
• Mesosphere- extends from 50-80 km above earth
• Coldest layer of atmosphere (low as -93 degrees
  Celsius)

5

• Thermosphere- farthest from earth surface, 80-550
  km above
• Hottest layer of atmosphere
• Nitrogen and oxygen absorb solar radiation
• Measured above 2000 degrees Celsius
• Greenhouse Effect
• Gases in atmosphere are like glass windows of car
• Sunlight that penetrates earths atmosphere heats
  the surface of earth
• Some heat bounces back into atmosphere and
  escapes
• Rest is trapped absorbed on earth by
  greenhouse gases gases that warm the air (water
  vapor, carbon dioxide, methane, nitrous oxide)
• Heat is bounced back to earth
• Greenhouse effect process in which gases trap
  heat near earth

6

• Good b/c keeps earth warm for life
• Bad when too many greenhouse gases are trapping
  heat Carbon dioxide and methane are in car
  exhaust, factory smoke, aerosol cans
• These gases will trap heat on earth and increase
  temperature on earth

7
Energy in the Atmosphere

• Energy from sun is transferred to atmosphere in 3
  ways radiation, convection, conduction
• Radiation transfer of energy across space and in
  the atmosphere
• Example stand in front of fire, feel heat from
  radiation
• Conduction flow of heat from warmer object to
  colder object when the objects are touching each
  other
• Example air near earth surface is heated by
  earth
• Convection transfer of heat by air currents
• Example hot air rises, cold air sinks

8
Heating of the Atmosphere

• Solar energy from sun reaches Earth as radiation
• Radiation is visible light, infrared radiation,
  and ultraviolet rays
• Only about 1 of this radiation from sun actually
  makes it to earth
• But it has a HUGE amount of energy
• ½ of this radiation reaches the earth surface
• Rest of radiation is absorbed by clouds, gases,
  dust
• Or is reflected (bounces back into atmosphere) by
  earths surface
• Earth surface absorbs heat, but why doesnt it
  keep getting hotter?
• Oceans and land send heat back into atmosphere
• Which will get hotter? Dark or light objects?

9
Movement of Energy in Atmosphere

• Weather is caused by constantly moving air
  upward, downward, sideways
• Cold air is more dense (heavier) than warm air
• So warm air rises, cool air sinks
• As air rises, it will begin to cool
• It eventually becomes more dense, and sinks back
  down to earth
• It heats back up, becomes less dense, and rises
  again
• This air cycle continues, called a convection
  current
• Convection currents are caused by the unequal
  heating of the atmosphere levels