 Extends from the Earth’s surface to outer space.  About 900 km (560 miles)  Mixture of gases, solids, and liquids

 Hydrogen and Helium were stripped away by solar wind early in Earth’s history  Outgassing – volcanic eruptions  First Stable Atmosphere  Contained 80% H 2 O vapor, 10% CO 2, 5 to 7% H 2 SO 4, and small amounts of N, CO, H, CH 4, and Ar

 Water in the atmosphere condensed and fell to Earth creating oceans (3.8 Ga)  Very primitive single celled life forms (3.5GA)  Nitrogen was the predominant gas (3.4 Ga)  Photosynthesis began with blue-green algae (3 Ga)  Oxygen builds up in the atmosphere

 At 2 Ga, ozone begins to form in the stratosphere  Increasing oxygen levels stabilized at ~20% (650 Ma)  Stratospheric Ozone was thick enough to protect Earth’s surface from UV radiation  Matter (C, O 2, H 2 O, N) begins to cycle as it does today between the atmosphere, hydrosphere, biosphere and geosphere.

 Nitrogen (N 2 )= 78%  Oxygen (O 2 ) = 21%  Argon (Ar) = 0.9%  Carbon Dioxide (CO 2 ) = 0.04%  absorbs heat in the atmosphere  All others = trace amounts

 Water vapor (H 2 O)  variable amounts (0-4% of volume)  absorbs heat in the atmosphere  Ozone (O 3 )  needed in upper atmosphere but is a toxic pollutant when in the lower atmosphere  Can be harmful to plants, humans

 Solids: Dust, smoke, pollen, salt, ice…  Liquid: water  Importance:  Seeds for clouds  Absorb or reflect solar radiation  Make pretty sunsets!

 Atmospheric layers based on temperature differences  Warm layers contain gases that easily absorb the radiant energy  Cool layers contain gases that do not absorb the radiant energy

 0 to 12 km  Means air “turns over”  Contains 75% of the atmospheric gases  Weather, clouds, smog  Average environmental lapse rate is 6.5°C per km (3.5°F per 1000 ft)  Hadley Cells  Wind currents directly influence ocean currents  Rising air = cloud formation; Sinking air = dry air

 12 to 50 km  Jet airplanes fly in the lower stratosphere  Jet Streams  a fast moving channel of air that controls the location of high and low pressure cells in the troposphere  Sub-polar and sub-tropical  Contains the ozone layer  3 O 2 + UV  2 O 3  Reaction absorbs most of the incoming UV radiation  Thickest at the equator, thinnest at the poles  Increasing temps above 20 km

 50 to 80 km  temps decreasing to -90°C with altitude  Meteors disintegrate in this layer  Little is known about this layer because it is above where research balloons and aircraft fly but below where satellites orbit

 80 to 450 km  Orbiting satellites  Temps increasing with altitude because of O 2 and N 2 absorbing high-energy radiation  contains the ionosphere – a layer of electrically charged particles  Divert cosmic radiation away from the equator toward the poles  Aurora result from cosmic radiation interacting with the ionosphere at the poles

 450 to 900 km  very little air here  Where the space shuttle orbits the Earth  Some orbiting satellites

 As atmosphere is heated, air molecules move with greater energy  Warm air is less dense (low air pressure)  Cold air is more dense (high air pressure) Cool Warm

 Heat = total kinetic energy of the molecules in a substance  Temperature = average kinetic energy of the molecules  Heat always moves from high to low temps

 Three mechanisms of heat transfer between land, water, and atmosphere  Conduction = transfer of heat through matter by molecules colliding (transfer by touching)  Convection = transfer of heat by circulation within a substance  Only in liquids or gases  Hot air is less dense  rises  Radiation = ALL objects emit EM waves  Does not need a medium (i.e. sun energy to Earth)  Hotter objects emit shorter wavelengths

 Scattering = incoming waves bounces off of the gas and aerosols in the atmosphere  Reflection = 30% of solar radiation is reflected back into space  Absorption = molecules absorbing energy increase speed (get hotter)  N 2 is poor absorber of radiant energy  O 2 and O 3 are good absorbers of UV energy  CO 2 and H 2 O are good absorbers of infrared  None of the gases are good absorbers of visible light

 Visible light is absorbed by land and water but reflected by snow and ice  The absorbed visible light is re-radiated back into the atmosphere as longer wavelength infrared radiation  Greenhouse gases absorb heat energy  H 2 O, CO 2, CH 4, N 2 O