The Atmosphere

							 The Atmosphere

Chapter 18: pgs 469 - 470
        S47-S52
             Composition
Composition of “dry” air
 78% Nitrogen
 21% Oxygen
 0.93% Argon
 0.038% Carbon dioxide

 Water vapor can vary from 0.01% - 4%
Structure
Structure of Atmosphere
 Troposphere - the lowest layer of the atmosphere,
  in which temperature drops at a constant rate as
  altitude increases, the part of the atmosphere
  where weather conditions exist.

 Almost all the water vapor and carbon dioxide in the
  atmosphere is concentrated in the troposphere.
 The temperature in the troposphere decreases
  6.5°C / km with increasing altitude.
Structure of Atmosphere
 Stratosphere - the layer of the
  atmosphere that lies between the
  troposphere and mesosphere in which
  temperature increases as altitude
  increases.

 Contains the ozone layer.
Structure of Atmosphere
Mesosphere - the coldest layer of the
 atmosphere, between the
 stratosphere and the thermosphere,
 in which temperature decreases as
 altitude increases. (-90°C)
Structure of Atmosphere
Thermosphere - the uppermost layer of
  the atmosphere, in which temperature
  increases as altitude increases.
Includes the ionosphere - where auroras
  occur.
Special thermometers have recorded
  temperatures of 1000°C!
                  Structure
Ozone Layer - layer of O3 in the Stratosphere that
 acts as a global sunscreen.
     - keeps 95% of UV radiation from reaching the
 surface.

Ozone Production:
3O2 + UV <--> 2 O3
        Weather vs. Climate
 Weather describes the conditions outside
  today. Climate is what you expect the
  conditions to be next year.
          Latitude and Seasons
 Since the Earth is a sphere, the suns rays strike
  the surface at different angles. The greater the
  angle of the surface to the sun the less intense
  the radiation.

 The tilt of the Earth causes changes in the
  angle of incoming radiation, resulting in
  seasons.
        Latitude and Seasons
 During which season is the earth closest to
  the sun?
 What if the earth did not tilt?
              Coriolis Effect
 Coriolis Effect – the curving of the path of a
  moving object from an otherwise straight
  path due to Earth’s rotation.
   Winds blow from high pressure to low pressure
    areas and curve as a result of the Coriolis.
   The Coriolis is stronger for larger, fast moving
    winds and is the greatest at the poles.
       Atmospheric Circulation
 Global Winds – each hemisphere contains 3
  looping patterns of flow called convection cells.
  The part of the convection cell that runs along
  the surface is called a wind belt.
      Atmospheric Circulation
 Tradewinds – prevailing winds that blow from
  east to west from 30 lat to the equator.
 Westerlies – prevailing winds that blow from
  west to east between 30 – 60 lat in both
  hemispheres.
 Polar Easterlies – prevailing winds that blow
  from east to west between 60 and 90 lat in both
  hemispheres.
      Atmospheric Circulation
 Doldrums and Horse Latitudes – Surface winds
  are weak.
 As the suns rays shift northward and southward
  during the changing seasons, the positions of
  the pressure belts also shift.

 Jet streams – a narrow band of strong winds
  that blow in the upper troposphere.
                  ENSO
 El Nino - Southern Oscillation - Every few
  years warm water builds up from Australia to
  South America changing upwelling areas as
  well as global weather patterns.
Normal Conditions
ENSO Conditions
Fig. S8-9, p. S51