SCIED 122 MIDTERM

• Significant gases composing Earth's atmosphere

  • Nitrogen
  • Oxygen
  • Water vapor
  • Carbon dioxide
• Composition of the atmosphere

  1. Nitrogen and oxygen occupy about 78% and 21% respectively

  2. Concentration of water vapor varies significantly

  3. Carbon dioxide is a small but essential component at 0.04%
• Earth's atmosphere


  • Relatively thin, gaseous envelope
  • Mostly nitrogen and oxygen, with small amounts of other gases
  • Shields the surface and inhabitants from the sun's dangerous ultraviolet radiant energy and material from interplanetary space
• Earth's atmosphere is unique from other planets in our solar system
• Greenhouse gases


  Water vapor and carbon dioxide trap a portion of Earth's outgoing radiant energy, keeping the average air temperature near the surface much warmer
• As atmospheric concentration of CO2 increases


  Average global surface air temperature increases
• Other greenhouse gases


  • Methane
  • Nitrous oxide
  • Chlorofluorocarbons
• Ozone


  A form of oxygen that absorbs much of the potentially harmful ultraviolet radiation from the sun
• Anything that reduces the amount of ozone in the atmosphere could affect the well-being of life on Earth
• Aerosols


  Tiny solid and liquid particles suspended in the atmosphere
• Troposphere


  • Lowermost layer where weather phenomena occur
  • Temperature decreases with increase in altitude
• Tropopause


  Outer boundary of the troposphere
• Stratosphere


  • Temperature increases with height due to ozone absorption of solar radiation
  • Maximum ozone concentration is observed near 25 km, but maximum temperature is near 50 km
• Mesosphere


  • Temperature decreases with height until the mesopause
  • Coldest temperatures in the atmosphere occur at the mesopause
• Thermosphere


  • Temperature is very high due to absorption of energetic solar rays by oxygen molecules
  • Temperatures vary day-to-day due to solar activity
  • Low density means air molecules have a very long mean free path
• Ionosphere


  Electrified region with high ion and free electron concentrations
• Exosphere


  Region where atoms and molecules escape Earth's gravitational pull
• Ionosphere


  Allows TV and FM radio waves to pass through, but at night reflects standard AM radio waves to Earth
• Exosphere


  Region at the top of the thermosphere where atoms and molecules shoot off into space
• Homosphere


  Lower, well-mixed region of the atmosphere where the composition of air remains relatively uniform
• Heterosphere


  Region from about the thermosphere base to the top of the atmosphere where diffusion causes heavier atoms and molecules to settle to the bottom and lighter gases to float to the top
• Atmospheric pressure


  The amount of force exerted over an area of the surface, decreases with increasing height
• Nearly all of the energy that drives Earth's variable weather and climate comes from the sun
• Rotation


  The spinning of Earth about its axis, producing the daily cycle of daylight and darkness

  
• Revolution


  The movement of Earth in a slightly elliptical orbit around the sun

  
• Earth is closest to the sun in January and farthest in July, but this difference plays only a minor role in producing seasonal temperature variations

  
• Factors affecting seasonal temperature variations

  • Gradual change in the length of daylight
  • Gradual change in the sun's angle above the horizon
• When the sun is directly overhead


  The solar rays are most concentrated and most intense
• The lower the sun's angle


  The more spread out and less severe is the solar radiation that reaches the surface
• The longer the path of sunlight through the atmosphere

  The greater the chance that sunlight will be dispersed, scattered and absorbed, reducing the intensity at the surface
• Inclination of Earth's axis

  The tilt of 23.5 degrees from perpendicular to its orbit, causing the seasons

  
• Summer solstice in the Northern Hemisphere

  June 21 or 22
• Winter solstice in the Northern Hemisphere

  December 21 or 22
• Autumnal (fall) equinox in the Northern Hemisphere


  September 22 or 23
• Spring equinox


  March 21 or 22
• Daylight length


  Decreases from 12 hours at the equator to higher latitudes
• The climate of the Philippines can be divided into two major seasons: the rainy season from June to November, and the dry season from December to May
• The dry season in the Philippines can be further subdivided into the cool dry season from December to February, and the hot dry season from March to May
• Temperature decreases with increasing height due to adiabatic cooling caused by expansion of air as it rises.
• The troposphere extends from the surface to an altitude of about 16 km at the poles and up to 20 km near the equator.