Chapter3 - Chapter 3 Atmospheric Energy and Global...

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Chapter 3 Atmospheric Energy and Global Temperatures Energy Essentials Energy Pathways and Principles Shortwave energy in from the Sun Longwave energy out from Earth Energy Patterns Energy patterns differ for deserts, oceans, mountain tops, rain forests, snow/glaciers Clear vs. cloudy weather can result in 75% difference in amount of energy reaching the surface Energy Essentials At Earth’s surface, solar energy intercepted by land and water surfaces, clouds, atmospheric gases and dust What happens to it? Basic Heating and Cooling Processes Radiation Transmission Reflection Scattering Refraction Transmission Conduction Advection Convection Latent Heat Radiation Process by which energy is emitted from a body Involves flow of radiant energy from body in the form of waves Hotter bodies more potent radiators than cool ones Hot bodies: more intense radiation and shorter wavelengths Temperature not the only control of radiation effectiveness Nature and substance of surface of object affects radiating capability Blackbody: a body that emits the maximum amount of radiation possible, at every wavelength, for its temperature Sun and Earth are blackbodies, i.e. perfect radiators Sun much hotter than Earth Emits 2 billion times more energy than Earth Terrestrial radiation waves are about 20x longer than maximum solar radiation waves
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Transmission Ability of a medium to allow rays to pass through it Earth materials are poor transmitters Sunlight absorbed at surface but does not penetrate Considerable transmission of sunlight in water Transmission sometimes depends on wavelength of rays Glass has high tranmissivity for shortwaves, but not long waves Closed car in sunlight will heat up quickly Glass lets shortwaves through Longwaves are reradiated from interior of car but cannot escape Vehicle gets hotter and hotter Atmosphere good transmitter of shortwave radiation, less effective transmitter of long wave Especially true when clouds, water vapor and dust exist Solar energy penetrates to Earth’s surface but reradiated long-wave energy is trapped in lower troposphere and again reradiated back towards the ground, where it is absorbed Earth’s surface and lower troposphere have higher average temperature Æ greenhouse effect Insolation Solar energy is unevenly distributed by latitude Fluctuates seasonally Global patterns of insolation at Earth’s surface differ from net radiation patterns at top of troposphere Examine map – deserts vs. rainforests Scattering Tiny particles and gas molecules in air deflect light waves and redirect them Wavelength is not changed Dust particles, pollutants, ice, water droplets and water vapor produce further scattering Some are backscattered into space but most reach Earth in altered direction Æ diffuse radiation Amount of scattering depends on
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This note was uploaded on 04/20/2008 for the course GEOS 200 taught by Professor Hanchette during the Spring '08 term at University of Louisville.

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Chapter3 - Chapter 3 Atmospheric Energy and Global...

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