Comprehensive Earth Energy Balance Model Overview
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Explore the Earth Energy Balance equation to grasp how atmosphere and Greenhouse gases impact Earth's temperature. Discuss one-layer and multi-layer atmospheric models to understand the intricate dynamics. Discover how different layers of the atmosphere and major Greenhouse gases contribute to the planet's energy balance.
Comprehensive Earth Energy Balance Model Overview
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Presentation Transcript
An improved energy balance model Goals: understand the effects of atmosphere and Greenhouse gases on the earth temperature.
Summary: Earth Energy Balance Equation Pin = Pout Pin = (1-A) S π REarth2, Pout = 4π REarth2 σ TEarth4 Tearth= 255K
Q1 Planet-X is at a distance R=2R_earth from the sun. its temperature should be A) 2 T_earth; B) T_earth / 2; C) T_earth /\sqrt{2}; D) depends on the radius of X-planet.
Green house effect • Model one: Glass layer effects on the earth temperature; • 2) An atmospheric model with Green house effect • (with Green house gases).
Q1 (facts) Atmosphere mainly A) reflects visible lights; B) absorbs infrared radiations from the earth; C) emits infrared radiation towards the earth; D) Both A), B) and C)
One-layer atmosphere model Assumptions: a) Atmosphere absorbs all infrared radiation from the earth; So that earth radiation not seen from outside. b) Atmosphere emits blackbody radiation.
σ Te4 Now the energy balance for the surface of the Earth is: • Pin = (1-A) S π REarth2+σ Te4 4π REarth2 • Pout = σ Ts4 4π REarth2
Now the energy balance for the surface of the Earth is: (1-A) S π REarth2+σ Te4 4π REarth2= σ Ts4 4π REarth2 • Ts4 = (1-A) S / 4σ + Te4 = 2 Te4 (Assuming Te = 255 K )
You should get Ts = 303 K = 30 ºC • Not really – too hot! Issues: • Is atmosphere a thin layer? • Is it totally absorbing in infrared?
Earth Energy Balance • The more complex models involving multilayer atmosphere partially transparent in infrared come up with better estimates of temperatures of the surface of the Earth – about 15 ºC