Composition of the atmosphere

• Composition of the atmosphere
  • Nitrogen (N) – 78%
    
  • Oxygen (O2) – 21%
    
  • Argon and other gases
    
  • Carbon dioxide (CO2) – 0.036%
    
• Variable components of air
  
  • Water vapor
    
    • Up to about 4% of the air's volume
      
    • Forms clouds and precipitation
      
    • Absorbs heat energy from Earth
      
  • Aerosols
    
    • Tiny solid and liquid particles
      
    • Water vapor can condense on solids
      
    • Reflect sunlight
      
    • Help color sunrise and sunset
      
  • Ozone
    
    • Three atoms of oxygen (O3)
      
    • Distribution not uniform
      
    • Concentrated between 10 to 50 kilometers above the surface
      
    • Absorbs harmful UV radiation
      
    • Human activity is depleting ozone by adding chlorofluorocarbons (CFCs)
      

Structure of the atmosphere

• Structure of the atmosphere
  
• Pressure changes
  
  • Pressure is the weight of the air above
    
  • Average sea level pressure
    
  • Pressure decreases with altitude
    
• Atmospheric layers based on temperature
  
  • Troposphere
    
    • Bottom layer
      
    • Temperature decreases with altitude – called the environmental lapse rate
      
    • Thickness varies – average height is about 12 km
      
    • Outer boundary is named the tropopause
      
  • Stratosphere
    
    • About 12 km to 50 km
      
    • Temperature increases at top
      
    • Outer boundary is named the stratopause
      
  • Mesosphere
    
    • About 50 km to 80 km
      
    • Temperature decreases
      
    • Outer boundary is named the mesopause
      
  • Thermosphere
    
    • No well-defined upper limit
      
    • Fraction of atmosphere's mass
      
    • Gases moving at high speeds

Composition of the atmosphere | Structure of the atmosphere | Earth-Sun relations | Atmospheric heating | Temperature measurement | World distribution of temperature | Links | top | Classes Home

Earth-Sun relations

• Earth-Sun relations
  
  • Earth motions
    
    • Rotates on its axis
      
    • Revolves around the Sun
      
• Solar Heating and Latitude
  
  • Relationship of Sun angle & solar radiation received on Earth
    
  • Daily paths of the Sun in the middle latitudes in the Northern Hemisphere
    
  • Seasons
    
    • Caused by Earth's changing orientation to the Sun
      
    • Axis is inclined 23½º
      
    • Axis is always pointed in the same direction
      
    • Special days (Northern Hemisphere)
      • Summer solstice
        
        • June 21-22
          
        • Sun's vertical rays are located at the Tropic of Cancer (23½º N latitude)
          
      • Winter solstice
        
        • December 21-22
          
        • Sun's vertical rays are located at the Tropic of Capricorn (23½º S latitude)
          
      • Autumnal equinox
        
        • September 22-23
          
        • Sun's vertical rays are located at the Equator (0º latitude)
          
      • Spring equinox
        
        • March 21-22
          
        • Sun's vertical rays are located at the Equator (0º latitude)
          
    • Characteristics of the solstices and equinoxes
      

Atmospheric heating

• Heat is always transferred from warmer to cooler objects
  
• Mechanisms of heat transfer
  
• Radiation (electromagnetic radiation)
  
  • Velocity: 300,000 kilometers (186,000 miles) per second in a vacuum
    
  • Consists of different wavelengths
    
    • Gamma (very short waves)
      
    • X-rays
      
    • Ultraviolet (UV)
      
    • Visible
      
    • Infrared
      
    • Microwaves and radio waves
      
  • The electromagnetic spectrum
    
  • Governed by basic laws
    
    • All objects, at whatever temperature, emit radiation
      
    • Hotter objects radiate more total energy per unit area than do cooler objects
      
    • The hotter the radiating body, the shorter the wavelength of maximum radiation
      
    • Objects that are good absorbers of radiation are good emitters as well
      
• Incoming solar radiation
  
  • Atmosphere is largely transparent to incoming solar radiation
    
  • Atmospheric effects
    
    • Reflection – albedo (percent reflected)
      
    • Scattering
      
    • Absorption
      
  • Most visible radiation reaches the surface
    
• Outgoing Radiation
  
  • Earth re-radiates radiation (terrestrial radiation) at the longer wavelengths
    
  • Longer wavelength terrestrial radiation is absorbed by
    
    • Carbon dioxide and
      
    • Water vapor in the atmosphere
      
  • Lower atmosphere is heated from Earth's surface
    
  • Heating of the atmosphere is termed the greenhouse effect
    

Composition of the atmosphere | Structure of the atmosphere | Earth-Sun relations | Atmospheric heating | Temperature measurement | World distribution of temperature | Links | top | Classes Home

Temperature measurement

• Temperature measurement
  
  • Daily maximum and minimum
    
  • Other measurements
    
    • Daily mean temperature
      
    • Daily range
      
    • Monthly mean
      
    • Annual mean
      
    • Annual temperature range
  • Mean monthly temperatures for Vancouver, British Columbia and Winnipeg, Manitoba
    
• Human perception of temperature
  
  • Important factors are
    
    • Air temperature
      
    • Relative humidity
      
    • Wind speed
      
    • Sunshine
      
• Controls of temperature
  
  • Temperature variations
    
  • Receipt of solar radiation is the most important control
    
  • Other important controls
    
    • Differential heating of land and water
      
      • Land heats more rapidly than water
        
      • Land gets hotter than water
        
      • Land cools faster than water
        
      • Land gets cooler than water
        
    • Altitude
      
    • Geographic position
      
    • Cloud cover
      • Clouds reduce the daily temperature range
        
    • Albedo

Composition of the atmosphere | Structure of the atmosphere | Earth-Sun relations | Atmospheric heating | Temperature measurement | World distribution of temperature | Links | top | Classes Home

World distribution of temperature

• Temperature maps
  
  • Isotherm – a line connecting places of equal temperature
    
  • Temperatures are adjusted to sea level
    
  • January and July are used for analysis because they represent the temperature extremes
  • Global temperature patterns
  • Temperature decreases poleward from the tropics
  • Isotherms exhibit a latitudinal shift with the seasons
    
    • Warmest and coldest temperatures occur over land
      
  • Isotherms show ocean currents
    
  • Annual temperature range
    
    • Small near equator
      
    • Increases with an increase in latitude
      
    • Greatest over continental locations
  • World mean sea-level temperatures in January
    
  • World mean sea-level temperatures in July