Annual-mean TOA radiation (ERBE, W/m2)

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Annual-mean TOA radiation (ERBE, W/m2)
Absorbed SW
Outgoing LW
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Surface temp (NCEP, oC)
January
July
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Surface wind (NCEP, m/s)
January
July
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Temperature (oC) and zonal wind (m/s) (NCEP)
January
July
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Temperature and potential temperature surfaces
J
T
decreases by 6oC/km
increases by 4oC/km
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Potential temperature (K) and zonal wind (m/s)
(NCEP)
January
July
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The bare rock temperature
In steady state, Ein Eout Ein p R2 S
(1?) Eout 4p R2 ? T4 R radius ?albedo
Putting it all together
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Radiative-convective equilibrium(Manabe
Strickler, 1964)
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CloudSW interaction
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CloudLW interaction
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Net cloud forcing from simple model(Hartmann, p.
74)
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Annual-mean cloud water path (g m2)
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Annual-mean total cloud amount ()
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Annual mean low cloud amount
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Annual mean middle cloud amount
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Annual mean high cloud amount
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Annual mean SW cloud forcing (ERBE, W m2)
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Annual mean LW cloud forcing (ERBE, W m2)
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Annual mean net cloud forcing (ERBE, W m2)
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Climate feedback the general ideaWhat happens
if we perturb the climate away from its
equilibrium,for instance by increasing CO2
concentration?






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• In the real world, both positive and negative
  feedbacks act simultaneously
• Overall, the negative feedbacks win otherwise
  temperature would run away to very high values
  (runaway greenhouse)
• However, the presence of positive feedbacks means
  that the temperature increase we get for a given
  increase in CO2 is greater than we would get in
  their absence more bang for the buck
• Dominant feedbacks
• Negative
• Planck (radiative) feedback
• Lapse rate feedback
• Positive
• Surface albedo feedback
• Water vapour feedback
• Cloud feedback?

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Ice albedo feedback

• As surface temperature increases, some of the ice
  in the polar ice caps melts, exposing ocean or
  boreal forest
• Ice is much more reflective to sunlight than
  ocean or forest
• So the feedback goes like this
• Increased CO2
• raises T
• melts some ice
• decreases reflectivity
• more insolation is absorbed
• raises T even further

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Water vapour feedback

• Relative humidity stays roughly constant as
  climate warms
• Since RH w/ws(T) and ws(T) increases
  exponentially with T, then humidity increases
  rapidly with T
• So the feedback goes like this
• Increased CO2
• raises emission level
• raises T
• raises humidity
• raises emission level even further
• raises T even further

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Feedback strengths in climate models (SodenHeld,
2006)
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Absorbed insolation
Insolation at TOA
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Absorbed insolation
Insolation at TOA
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SHF into ground!
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The moist equations of motion
evaporation
condensation
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Energetics
Total energy per unit mass

• Rate of change of
• kinetic energy
• potential energy
• thermal internal energy
• latent internal energy

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Energetics
Rate of change of total energy per unit volume
but
Finally
Note that
moist static energy
small
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Seasonal cycle of surface temperature
Amplitude of seasonal cycle (oC)
Temp (oC)