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SIO209 Cloud Climate Feedbacks. Scripps Institution of Oceanography University of California. Dr. Piotr J. Flatau [email protected]. SIO209 Clouds. SIO209 Clouds. SIO209 Clouds. SIO209 Cloud Climate Feedbacks. Radiative Convective Equilibrium Feedbacks Cloud Physics Feedbacks - PowerPoint PPT Presentation
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Dr. Piotr J. Flatau
Scripps Institution of Oceanography
University of California
SIO209
Cloud Climate Feedbacks
SIO209
Clouds
SIO209
Clouds
SIO209
Clouds
SIO209
Cloud Climate Feedbacks
• Radiative Convective Equilibrium Feedbacks
• Cloud Physics Feedbacks
• Cloud Formation Feedbacks
SIO209
Cloud Climate Feedbacks
• Radiative Convective Equilibrium Feedbacks
• Cloud Physics Feedbacks
• Cloud Formation Feedbacks
SIO209
Radiative Convective Equilibrium - Examples
Clear sky energy balance (IR cooling)
Mid morning max. precipitation in tropics
Observed temperature differences between fall and spring Stratocumulus balance (subsidence, heat flux, IR cooling)
Convection control of SST in the tropics
Lapse rate stabilization or destabilization
SIO209
Radiative Convective Equilibrium – IR cooling
-100 W/m2 IR cooling RCE
(“W. M. Gray”)
SIO209
Radiative Convective Equilibrium - Definition
To first order, the atmosphereexists in a state of quasi balance between
radiativecooling and the convective processes that give
riseto latent and sensible heating.
SIO209
Radiative Convective Equilibrium - 1K/day
Radiative cooling - clear sky
dT/dt = - F/(cp rho Dz) =-100/(1004 *1.2* 8000) [K/s]= -100/(1000 * 8000) *(60*24*60)=36*24 10^4/ 8*10^6=36*24/(800)=36*4/100 =about=
1.0K/day
SIO209
RCE - Up Moist Down Dry
Evaporation
Q=mL= 1g * 2.5 * 10^3J/gF=2.5* 10^3/(24*60*60)= 1/36 W/cm2=1000/3.6 W/m2=250W/m2
L=2.5*10^6 J/kg1W=1J/s
0.3cm evaporation per day to offsets 100W/m2 of IR cooling
SIO209
RCE Example: Precipitation in Tropics
SIO209
Early Morning Precip Max in Tropics - RCE
Mapes, 2002
Hartmann & Larson, 2002
Implications for deep convection
SIO209
Stratocumulus RCE
SIO209
Lilly’s Model of Sc. RCE
dT/dt=-4 K/day (IR)Subsidence (30mb/d-100W/m2)Heat flux
d T /dt = - (Fnet,base-Fnet,top)/ (cp rho dz)
Fnet,top=75W/m2Fnet,base=15W/m2
Cp=1004 J kg^-1 K^-1Rho=1.2 kg m^-3Dz=1km
SIO209
Radiative Convective Equilibrium – SST Control
SIO209
Radiative Convective Equilibrium – SST Control
SIO209
Radiative Convective Equilibrium – Thermostat
SIO209
Radiative Convective Equilibrium Adjustment
SIO209
Radiative Convective Equilibrium – Summary
