EATS 1011 Lecture 10

Clouds

Nacreous clouds

• A form of PSC (~10 microns)
  
• Formed by waves over mountains
  
• Text and other locations: nacreous clouds
  
• PSC
  
  • Polar stratospheric clouds
    
• Located about 15-25km
  
• Winter polar stratosphere is very cold 180-190 K
  
• HNO₃ and water form ice clouds
  
• Ice surfaces catalyse conversion of HCL to CL which attacks ozone and creates ozone hole
  
• Contains:
  
  • H₂O, h2SO₄, HNO₃, HCL
    

Noctilucent Clouds

• Only appear in polar regions
  
• Size ~.1 microns or smaller
  
• Very thin layer clouds:
  
  • Hard to see over head
    
  • Only visible at twilight or later w/ a long path for illumination
    
• At the summer mesopause
  
• Very cold ~100-140 K
  
  • 173 to 133 degrees celcius
    
• Frozen water
  
• Ccn probably meteoritic dust
  
• Wave structures revealed in ice formation
  
• Can be warning of increased methane (CH₄)`
  

Lapse Rates

• Environmental
  
• Γ_e environmental lapse rate
  
  • dT/dz = ΔT /ΔZ = - Γ_e
    
  • 'dry' adiabatic
    
    • g/C_p = Γ_dry
      
  • 'moist' adiabatic
    
    • g/C_p = Γ_moise
      
  • Γ_Moist < Γ_Dry
    
• Depends on the planet and the major gas
  
• AIR PARCEL(AP)
  
  • Think of an isolated unit of air maintaining its integrity
    
  • This doesn't work for long because of exchange of molecules etc
    
• Lapse rate is how the temp is going to change in height
  
• A steep lapse rate means large temperature change
  
• Adiabatic
  
  • No exchange of energy with outside
    
• Cooling
  
  • Important in Cloud formation and rain
    
• Mean global rate
  
  • ~6.5 C/Km
    
  • Inversion, temperature increases with height
    
• Specific heat @ constant pressure C_p energy add to raise temp 1Celsius for 1kg @ constant pressure
  
• Specific heat @ constant Volume C_v energy add to raise temp 1Celsius for 1kg @ constant pressure
  
  • C_p(air) = 1007 J/kg/Kelvin
    
    • For one Kg you have to have supply 1007 joules for 1 degree celcius difference
      
  • C_v(air) = 700 J/kg/Kelvin
    
• − T2 ) / (Z2 – Z1) = (-g)/Cp
  
  • Dry adiabatically
    
• -(T₁MC_p)
  
  • Extract heat
    
• + Mg(z₂-z₁)
  
  • Add potential energy
    
• + CpMT₂
  
  • Add heat