Eats 1011 Lecture 6

ITCZ - intertropical Convergence Zone

ERBE – Earth Radiation Budget Experiment

• Designed to study the radiative energy
  
• Measures radiation coming from the atmosphere
  

Tropics

• Solar heating is greater than IR cooling
  

Polar Regions

• Solar heating is less than IR cooling
  

Heat transfers between the two to stop the earth from getting really hot in some areas and really cold in others

 

Water Vapour in the Atmosphere

• Mixing ratio
  
  • Troposphere is between 10^-2 to 10^-5 by volume or mass with most in the lower troposphere
    
  • Global average ~2.5*10^-3
    
  • Stratosphere 4*10^-6 by volume
    
• Latent Heat
  
  • Energy is required/released for a phase change
    
  • Heat storage when liquid converts to vapour
    
  • Heat release when vapour turns to water
    
    • L_v – vaporization – 2.5 * 10⁶ J/Kg
      
    • L_f – fusion / freezing – 3.3*10⁵
      
    • L_s – sublimation – L_{u +} L_f – 2.8*10⁶
      
      • Energy required / released when 1Kg of material changes state
        
• To calculate the amount of energy required for evaporation
  
  • Need mass of water
    
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    • 2cm = 0.02m rain (over each m²)
      
    • Density water, p_w = 1000kg/m³
      
    • Mass = 20kg/m²
      
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    • Mean water mixing ratio ~
      
      • Mass water =
        
    • Removal rate is estimated from the globally average rainfall ~ 1m / year
      
    • This is equivalent to about
      
    • Mass over 1m² ~ /m²
      
    • = 1000 kg/m²
      
    • Turnover time
      

t_residence = (25kg/m²) / (1000 kg/m² * year)