California State University Long Beach

GEOL 300i; Earth Systems and Global Change
Lecture 7

Dr. Rick Behl

Atmospheric structure (layering)

Primarily distinguished by temperature

• Thermosphere (>80 km, hottest)
  
• Mesosphere
  
• Stratosphere
  
• Troposphere (lowest, contains 90% of the air and almost all of the weather)

---

The Greenhouse Effect

• Transparent to incoming ultraviolet (UV) radiation, yet absorb outgoing infrared (IR) radiation
  
• H₂O vapor
  
• CO₂
  
• CH₄
  
• etc.
  
• As these gases absorb energy, the troposphere is heated

Global atmospheric circulation

• Solar radiation is the driving force behind all atmospheric and oceanic circulation
  
  • Imbalances between poles and equator
    
  • Redistribution of excess equatorial heat
    
  • Primarily in Troposphere (~11km altitude)
  
  
• Hadley Circulation Model... a first attempt
  
  • Rising air in tropics, sinking at poles
    
  • Three-cell Model... modified Hadley's model
    
    • Rising air at equator and 60 degrees north and south
      
      • "Weather equator" is actually a few degrees north of the geographic equator
        
      • Termed the Intertropical Convergence Zone (ITCZ)
      
      
    • Sinking air at poles and 30 degrees north and south
      
    • Add Earth's rotation and coriolis effect to explain surface winds pretty well
      
      • Coriolus effect
        
        • Right in the northern hemisphere
          
        • Left in the southern hemisphere
    
    
  • Winds at the earth's surface
    
    • Tradewinds
      
    • Westerlies
      
    • Polar easterlies